Everything ends up tiled eventually but it is not that difficult to tack on some real time decoding (there are many libraries that do it for you) and use a standard format.
I think PCX is most common :S Atleast with GBA...
When I did some small games, I made pictures in photoshop, which had to be saved as PCX and then converted to a h-file and a c-file (C (prequel to C++) and it's header)...