http://flif.info/another image format that seems to do a lot, but what i'm interested is the "smaller than PNG" and "outperforms PNG" part.
because, I know i've said PNG is slow as hell many many many times and have always stayed away from PNG for that reason. and the progressive loading might be handy for just skipping the picmip resampling step for lower detail on texture load.
Though now i'm worrying about memory usage and how it behaves on the ideal Pentium 200 target
EDIT: GPLv3 sucks, so can't really integrate their reference implementation