This is epic, are you using gimp, or paint to color it? I'd recommend buying a tablet, and pain tool sai, they are really awesome for coloring stuff, and actually easier. :U But that's just my opinion. Your art is already amazing, just think about how awesome it would be if you could use a tablet with this. But your art is really improving, you're good at coloring it.
It gives you a download. If it's a regular tablet, it's probably produced by Wacom, and a Bamboo model but to be safe on your version, check the serial number and such on the bottom. P.S. If it is from that website, it's free.