some help for a newbie maybe?

I'm new to all this graphic stuff, and I want to make some sigs to use on other forums, but they always get very plain and boring when I make them, so does anyone know some cool effects to make 'em look a bit less plain?

here's my newest creation:
Shadow the Hedgehog

and here's my best one so far IMO:
Ghost in the Shell

if it´s plain, it needs more stuff. lol..simple fact.
Just add details.. If you like trendwh00r, just put some of that usual crap, microtext, grid, scanlines, little "+" - signs..
If you like the grunge-style, brush it up, put a treshold layer on it and erase it almost away...u know, all that crap..

Plain isn´t always a bad thing, depends on the style.. Your hedgehog-thingie looked ok with being a bit on the empty side IMO... Don´t force stuff on it, unless it is really called for.