It's the end of the world as we know it

Has anyone used GIMP for icon and banner making? Is it doable? I'm giving it a try because Photoshop isn't within my budget right now, and I couldn't really justify getting it for what I want to do. That is, not much. But it seems I've developed an interest in icon making, and I'm trying to learn some rudimentary skills. I've been looking at some tutorials, mainly on icon_tutorial on LJ, but any references or suggestions are appreciated.

I really wanted some Hope Springs icons, and a banner. But since I think I might be the only active person in the fandom, I've decided to try to make some myself. The icon for this post is an initial attempt. It's not wonderful, and I only tweaked the coloring of an already-decent screencap. Other screencaps are giving me some difficulty. But I shall persevere.