A bit of emptyness is fine, but don't make that space tooooo empty (aka plain black

).
Fill it up with brushes or what ever, use colours that are soft to the eye, so you do see them, but they don't ruin the flow.
I personally think that signature needs some work though >.>
It's mainly a simple render on a black background without anything custom (or rarely).
This doesn't go for photomanip tho, that's all about trying to make something look good (or different). But instead you try to make it look as if it was supposed to be like that.
Like this:
But at the end it all comes down to personal taste, I know.
Greetz, Miyo