Whoa! For a first sig, that is pretty darn good. Seems as if you already have a lot of the components of a sig working for ya'! But yeah, here are some quick tips. ;D

- A smooth border on your render (in this case Luigi) usually helps make your sig "flow" more.

- This is just a personal one, but I usually like to have the background have the same colors, or at least close to it, as the render. Just a way to prevent the render from standing out too much I guess. ;D

But, nice border around the sig, and the test looks fine! Your off to a nice start. :D