You really want to try and get hold of photoshop, Gimp really doesn't compare.
As for your work so far, and why no one's commented on it, I'll break it down, I know you're limited because you only have gimp.
But all you've done is put poor text, on a bad background, and added a cut onto it to make a sig. There's not a lot anyone can say about it.
So people probably aren't saying anything as to not offend you.