Alright, I'll take it as you posted it:
right now I think it's way too big for a signature. Therefore I'd make it smaller. :P
The particle brush is too apparent imo. Looks like you only used 2-3 different ones. I'd put in more diversity, maybe play some more with colors (since you got the blue line there).
But for a first try? I dont think thats too bad, honestly.
Oh, and could have polished that text more. looks a bit boring but you will learn :P