@tty This is the test I did:

I have a 90kb rom, of which only 64kb is the program space, what I do is read the rom file with the file device, until I reach the end of the rom data, then I drew a picture that was stored at that location to the screen.

It's a bit clunky right now because I must know the name of the rom, which is a bit fragile, but if I can find a way around that, I might be able to package roms with lots of assets as a single rom.