Well, I've been having problems with making my very own custom sprite graphics for my game. But, is it morally wrong for me to use Ben Croshaw's graphics as a base template? I love his art out of all the graphics I've seen in an AGS game. They're just so simplistic and NES-ish, yet serious. It just troubles me to wonder if doing this is alright.
Here's a sample of what I've done.
My creepy surgeon based off Trilby's temp:
(http://img280.imageshack.us/img280/4762/surgeonnn7.png)
It's not morally wrong, but it may not advance your skills as fast as making characters from scratch. Also, if this sprite is something you want critique on this post should be in the critics lounge.
You may have difficulty matching sprite style to background style if you "cheat." As a crappy artist (tm), I do a lot of tracing, and then try to take what I like/learn to another drawing. It hasn't made me a great artist, so I don't know if I recommend it, but it's much more difficult to rip off backgrounds than characters. Try thinking about what you like/don't like, and what attributes go into those characteristics. Try making sprites with the same head:torso:legs ratios and experiment.