Change the background wallpaper

If you have a Windows system, copy your 800x600 or 1024x768 .bmp or .jpg file to the \_ISO folder on your E2B USB drive and run \_ISO\E2B_Editor.exe. This will allow you to set the background picture and many other options and then save the changes to the \_ISO\MyE2B.cfg file.
Tip: If you want to test a variety of .bmp or .jpg wallpaper files, simply copy them to the \_ISO\MAINMENU (or any) menu folder and select one from the E2B menu (v1.A1+).

Use a \_ISO\mybackground.bmp file

If you don't edit the MyE2B.cfg you can copy your own mybackground.bmp or mybackground.jpg file to the \_ISO folder (you can compress a .bmp using 7Zip by selecting gzip as the compression type to reduce the file size for faster loading - or use the E2B LZMA_Encode.cmd script for even greater compression).
You can download wallpapers from here - resize them to 800x600 using Microsoft Paint and save as '\_ISO\mybackground.jpg'.

Add\edit the MyE2B.cfg configuration file

Alternatively, rename the \_ISO\Sample_MyE2B.cfg file to \_ISO\MyE2B.cfg (if one does not already exist) and change the following entries to point to your own wallpaper...
# set graphics mode - use 640, or 800 or 1024 - or specify full mode - e.g. 800 600 24 = 800x600 x 24-bit colour
set GMODE=800
set MYWBMP=/_ISO/myspecialbackground.bmp
IMPORTANT: Use forward-slash / instead of \ in paths. grub4dos is like linux and uses / instead of \. 
The MyE2B.cfg file must start with !BAT on the first line because it is actually a grub4dos batch file.
Later versions of E2B also support .jpg files as well as .bmp files (save  as .jpg using Microsoft Paint to ensure they are in the correct format or else it may not load).
E2B will look use the specified file if it can be found, otherwise it will use the default E2B background.

Note: The file extension is not used by grub4dos to determine it's type - you can have a gzip compressed bitmap called fred.zzz or a JPEG file called doris.bmp, if you wish!

If you want to use your own background file (e.g. 640x480 or 800x600 or 1024x768)  ensure that the .bmp size is exactly correct (e.g. 800x600 and not 800x599 or 799x600).
Resolutions above 1024 x 768 are not supported by E2B because E2B uses memory in the same area as grub4dos stores large bitmaps and it may crash grub4dos!

You need to set GMODE correctly (default is 800 and is suitable for 99% of systems), some examples are:
set GMODE=800                 (800 by tallest available in highest colour mode) *RECOMMENDED*
set GMODE=800 600           (800x600 in highest colour bit depth available)
set GMODE=1024               (1024 wide by tallest available by highest bit depth available)
set GMODE=1024 768         (1024 wide by 768 by highest colour bit depth available)
set GMODE=800 -1 24:32    (800 by tallest available that is 24 or 32 bit colour - uses highest available)
set GMODE=800 600 24:32 (800 by 600 by 24 or 32-bit colour - uses highest available)

for your MyE2B.cfg file. The menu size and help text position will need to be changed too if you change the resolution. 
I strongly recommend you do not use higher than 800x600 because not all systems can support these higher resolutions (e.g. early netbooks are 800x600).
If you use 640x480 or 1024x768, the menu settings for number of menu items, menu width, etc. may also need to be changed because you can get more text lines and columns on a 1024x768 screen.
Note: If the file \_ISO\MainMenu.bmp or \_ISO\MainMenu.jpg is present, the file will be loaded just before the Main Menu is displayed, thus overriding any setting of MYWBMP which may be set in the MyE2B.cfg file - see here for details (E2B v1.A1+).

Use an alternate MyE2B.cfg file

If you use 1024x768 in your MyE2B.cfg file, you may find that certain netbooks, etc. do not support that resolution.
You can use the following lines in your MyE2B.cfg file to check if the system does not support 1024x786x24 graphics mode and thus use an alternative configuration file:
debug 1 ;; vbeprobe > (md)0x220+5 ;; debug 0
cat --locate=1024x768x24 (md)0x220+5 > nul || /MyCSM800.cfg && goto :EOF
debug 1 ;; vbeprobe > (md)0x220+5 ;; debug 0
cat --locate=1024x768x24 (md)0x220+5 > nul || /_ISO/MyE2B800.cfg && goto :EOF
You can then add a MyE2B800.cfg file containing all settings for 800x600 which will be used instead of the MyE2B.cfg file. Ensure the first line of the cfg file starts with !BAT.
Note: E2B also supports GFXBoot menus.
Tip: Choose a bitmap that has a clear area at the bottom so that the help text is easily visible. Avoid a multi-coloured, high-contrast picture (e.g. lots of different bright colours and dark blacks) as it will be difficult to choose a text colour that will stand out against all of the colours in your picture! Another idea is to use a bitmap editor and draw a filled rectangle over the picture so that the menu can be displayed within the rectangle. A clear area for the menu help text underneath the menu is also a good idea. You can also add your name or company name or company logo to the bitmap itself or add a STAMP. See the Gallery for ideas.
You can use the settings in MyE2B.cfg to change the menu position and the menu size, text and border colours. 

Menu Editor

Use the E2B_Editor.exe GUI to design your menu (800x600 or 1024x768 only).
You can, of course, make a plain single colour 800x600 bitmap for the background (see 'Background fill colour' below).
Tip: grub4dos does not support all possible types of JPG or BMP files. If the background does not look correct, then simply load it into Microsoft Paint and re-save it as a 24-bit colour .bmp or .jpg file.
Lots of wallpapers can be found here!

Background fill colour

E2B v1.78+ also support filling the entire screen with a single colour. This is much quicker than loading a wallpaper file.
The MYWBMP value must start with 0x followed by a 6-character hexadecimal string (RRGGBB):

# fill 800x600 display with red pixels : R=FF  G=00 B=00
set GMODE=800
set MYWBMP=0xFF0000
Note: STAMPs should only be used after loading a .jpg or .bmp wallpaper. If you want STAMPs on a plain background, you must load a plain colour graphics file first.

Use a JPEG file

E2B v1.72+ also supports .JPG files for use as wallpaper backgrounds as well as .bmp files.
I recommend working on an image in 24-bit .bmp format and then converting it to .jpg as the final step. Progressive (web format) JPG's are not supported (these are often used for websites as they contain a low-res image + hi-res image). If the .jpg does not work in E2B, load it into Microsoft Paint and re-save it as a .jpg file to convert it into a non-progressive JPEG format.
You can specify the name of your .jpg in the \_ISO\MyE2B.cfg file or simply name the file as \_ISO\MyBackground.bmp or MyBackground.jpg and it will be used by default.  Only grub4dos 0.4.6a supports .jpg files (grub4dos 0.4.5c does not support .jpg).

Background for a Master password entry

When E2B boots, you can configure it so that the user must enter a password before the Main menu is displayed.

You can have a different background for a Master Password entry screen - see here.

Changing background based on the day of the week

Add the lines below to your \_ISO\MyE2B.cfg file. Ensure that you have seven .bmp.gz files in the \_ISO folder named Aurora0.bmp.gz to Aurora6.bmp.gz.
# get day of week
checktime | set A=
set /a dow=%A:~20,1% > nul
set A=
# we now have a number between 0 and 6 (0=Sunday, 6=Saturday)
set MYWBMP=/_ISO/Aurora%dow%.bmp.gz
set dow=

Check for December

Use this in your MyE2B.cfg file to load a different bitmap for December
checktime | set A=
set  /a month=%A:~5,2% > nul
set A=
# 1 = January, 8=August, 12=December
if %month%==12 set MYWBMP=/_ISO/XMAS.jpg
Note: %day%, %month% and %year% are already available in later versions of E2B.

Random background

Add the lines below to your \_ISO\MyE2B.cfg file. Ensure that you have three .bmp.gz files in the \_ISO folder named Aurora1.bmp.gz to Aurora3.bmp.gz.
# get a random number between 1 and 10
set /a randnum=%@random% / 3277 + 1 > nul
# if greater than 3 then get another number!
if %randnum%>=4 goto :rlp
# we now have a number between 1 and 3
set MYWBMP=/_ISO/Aurora%randnum%.bmp.gz
# could use set GFX=message%randnum% instead
set randnum=

%@random% returns a number between 0 and 32767, so dividing by 3277 will give a number between 0 and 9.

Backgrounds for sub-menus

You can have a different background for each sub-menu - see here.

Write text strings to the menu

You can write text strings to the menu screen by adding lines to MyE2B.cfg, e.g.

# Write text to the menu (grub4dos 0.4.6a only) - --string=x=y=colour="text"
setmenu --string=69=18=0xFF00FF="Hello"