Everyone hits that point, myself included. Try to find a style that you like, some people enjoy old, antique graphics, when others like myself, like glassy, sleek ones. Then try to fiddle around in the tutorial section as BB said, you'll eventually get something you like and can add your own twist to it.
I really like this tutorial if it interests you:
http://paintdotnet.12.forumer.com/viewtopic.php?t=3031