That's not bad for your first signature. I like how you didn't stuff it with brushes like the typical beginner would do. Text could be better (if it's just to stop people from ripping, then it's okay I guess). I don't get what the thing is in the top right, and isn't really needed. Face is cut off on the right.
Did you take a render and place it over some green plants?
For your first, 8/10 for creativity.