This is the BACKIMG file format for GBAMP

Pallettes: These are stored as a series of 1024 bytes. Every 4 bytes represents a colour in the colour table, in BGRN format (blue, green, red, null). This makes for a total of 256 colours. It is not advisable to use the last two to four entries, as they may be replaced with the text colours. The first entry will be transparent for icons.

Background Images: These are stored as a series of colour table indicies. The bytes are in left to right, top to bottom order, making up 160 rows of 240 pixels. These are 38400 bytes long. These each use their own pallette, stored immediately before the image.

Main Screen Icons: These are like the Background images, except they are 64x64 pictures, 4096 bytes long. These use the same pallette as the Main Screen background.

File select Icons: Same as above, except 16x16, 256 bytes, File Select pallette.

Font Colours: These are stored as an RGBN colour.

Main Screen Icon Positions: Stored as two bytes, XY, offset relative to top left of screen

File Select Text Position: Stored as above, except is start of text, not of image

Help Text On/Off: Stored as two bytes. 0000 = off, anything else = on.

Offsets:
These are in Hexadecimal format, use a calculator to convert to decimal if need be.

00000	Main Screen Pallette
00400	Main Screen Background
09A00	Movie Icon Picture
0AA00	Music Icon Picture
0BA00	Pictures Icon Picture
0CA00	Game Icon Picture
0DA00	Ebook Icon Picture
0EA00	File Select Pallette
0EE00	File Select Background Image
18400	File Select Folder Icon
18500	File Select Previous Icon
18600	Text Screen Pallette
18A00	Text Screen Background
22000	Music Player Pallette
22400	Music Player Background
2BA00	Help Icon (Main Screen) Picture
2CA00	Menu text colour
2CA04	Highlighted text colour
2CA08	Text Colour
2CA0C	No Observable effect
2CA10	Movie Icon Postion
2CA12	Music Icon Postion
2CA14	Image Icon Postion
2CA16	Game Icon Postion
2CA18	Ebook Icon Postion
2CA1A	Help Icon Postion
2CA1C	File Select text offset
2CA1E	Help Text On/Off