Yep, it's not easy. The problem is though, it dates very easily. After a few years, you'll look back and say "Ugh, not more bloody cheapo lens flare" or "Ugh, you could make that lok much better with Photoshop 17"
A classic example is Carlos Ezquerra's first stuff on Wilderlands (I think). Those horrible 'square' backgrounds. The photo stuff he used for backgrounds was not bad at all, although a mate who's an artist (not a comic one) thought it looked awful. So yeah, it dates very quickly.
As usual I'll list Fabry's, Belardinelli's old ultra-detailed B&W art, which will always inspire cos it's so damned good! But again, fully painted stuff too, although style I suppose will indicate dating also.
Anyhoo, I've wittered enough. Yet again we get sucked into the coloured artwork thread!