A few character designs I find inspiring:
Designs from a French artist I found on Deviant Art. Her characters are deceptively simple, distinct, and stylish.
Gorillaz band members drawn by Jamie Hewlett. His characters are stylized and flat, but still animate-able and very, very distinct.
And of course, Chris Sanders. His characters are dynamic and eccentric, and his girls are all sexy.
I've always loved the aesthetic of Shag; his characters are flat but dynamic, expressive, and extremely stylish. I feel like his style (including his color palette) would be great reference for Flash animations.