wowza, thats pretty sensational. Still feels like its missing something, some contrasting colour perhaps? Also, the text doesn't really fit. You have the right style and colour but it seems to large, maybe try it smaller and more spaced out and placed on the right side. edit : Just realised that it needs some more perspective and depth, some subtle dodge and burn tooling should sort that out.
Does gimp have the burn and dodge tool? Never really used it, if not then just use white and dark soft default brushes and either lower the transparency or adjust the layer setting. Its usually better if you do it bit by bit and use different techniques. Its got the potential to be a great, unique sig.
Well I used them all the time when I made sigs, they're great for adding depth and perspective. A lot of people's sigs appear flat and therefore its difficult to suspend disbelief and pretend that whatever seen they have created on their canvas looks real. For instance, with your signature here to me it looks like some kind of alien forest/jungle. However it also looks flat and therefore I don't suspend belief and I can't stop thinking 'thats been made in ps/gimp'. Thats probably the 'something missing' i mentioned earlier. Anyway, I you understood that psychological waffle, otherwise I'm not going to do so well in my exams this year.
Ha ha ha, yeah, Burn and Dodge tools in GIMP are rarely used by anyone I've talked to. Also, I want to know what your technique for the lightning is. As for the sig, it seems too busy, and for some reason I'm not quite liking it.