It's an MS Paint one, I don't know how to use Photoshop or GIMP, bear with me here.
You should learn how. I can't even begin to describe how downloading gimp can help with you work.
For paint it's not that bad I guess. :p
I don't even know how to use paint like that acctually, good job. I use GIMP, my current sig was made for me but i added the rain effects, you should deffinately download GIMP and then you could read some easy tutorials,its not that hard and its free!