These are my second and third ever sigs that I made with GIMP for a friend. Both of these weren't too difficult, but I just took my time with making them and trying to make them look perfect.
Keep it up man, Gimp is quite hard to work with at first, it gets easier though. Try to find some tutorials or just fool around with it. You'll be surprised with what you can do.
The background areas on the first signature are kinda dark. Try to read more tutorials and u'll learn a lot from it. Also work on your text..