Kingcom is right, these are all extracted from a .bin file inside a working Gamecube ISO using a custom tool.
The file is packed with graphics files (namely SPR files containing backgrounds) among others, so I'm inclined to believe these BMP files are proper image files with a funny format.
I imagine corrupted image data would look wrong around specific sections of the image, rather than the whole thing looking like pixel confetti. Then again, I've never run into something like that.
I was wondering if Dolphin's code wouldn't have something to deal with these files, thanks for finding it! I'll give it a thorough look later
I think I found the format for the files with "type" 06. Images are divided in 8x8 tiles:
(ignore the faulty palette)
It goes like:
bytes 0 - 2: "BMP".
byte 3: type? palette number? 06, 07, 09 or 0a.
bytes 4 - 7: number of colours in palette.
bytes 8 - 11: width (divide by 8 to get number of tiles in a row)
bytes 12 - 15: height (divide by 8 to get number of tiles in a column)
bytes 16 - 31: all zeroes.
I'm beginning to wonder how to edit tiled images...