Very cool.
I have no artistic skills, yet even I can make a logo. So unless your art is of a very high standard (ie Mobius) I doubt anyone will actually pay you for it.
Don't let that put you off, I remember when Mobius joined the forum, he said he had just got photoshop and was going to learn to use it, then started making signatures for everyone. Now look at what happened. If Mobius can get as good with art/photoshop as he is, I am sure anyone (even me) can do it.
EDIT: As an example of what practice can achieve, here's one I did a while ago. I can't remember how long it took me, I probably spent a few days working on it
So keep working on it, and keep getting better.
