I don't know where to start with this. I kinda like the pastel colours in the background however they don't fit with this particular signature. The mario character is lower opacity, or a blending mode, that's wrong, it makes it look a really noviced sig. There is no flow apparent. I can't judge the lighting, nor the depth. If you're a beginner it's not bad, it's a good start. Try to keep your render/stock 100% opacity and use effects around and on the top of it. Try using some filters. Also, i'd advice you to try using real life stocks, they're a lot better IMO. Nice try anyway, if you need more help msn me.
i think its too bright like the whole sig is just too bright you should make some contrast in the sig
Its great but the like BH the opacity on mario is to low and the background is a bit plain good work for GIMP though