Thanks for the comments - constructive criticism doesn't make me angry. I'd much rather have that, than a load of sycophants saying it's wonderful just to get a sig impression.
Thumb quality is probably a result of me being miserly and over compressing - I've probably got the lowest b/w bill on this board.
I think the black came during a fetish site building phase, and it followed a green background which wasn't working. I really prefer yellow, but I might try a background image instead. And I also know I should add more text even though it's called good thumbs.