The \_ISO\docs\Templates folder in the E2B download contains examples of various 'Themes' or 'Skins'.
Just copy the files from one of the folders under Templates to your \_ISO folder (or read the ReadMe.txt file if one is present).
The \_ISO\MyBackground.bmp file (exact name) will be used if no valid MYWBMP variable is used in the MyE2B.cfg file.
The MyBackground.bmp file can be in JPEG or BMP format. It can also be compressed using GZip or LZMA_Encode.cmd. Note: Even if the file is a compressed JPEG file, it must still be named 'MyBackground.bmp'.
If a GFXBoot menu file is specified using the GFX variable, the path will be relative to the \_ISO folder (e.g. set GFX=docs/Templates/GFXMenu/message)
To add a Main menu entry to test many different Themes, read the \_ISO\docs\MyThemes\ReadMe.txt file.