I have got a lot of mine from here.
http://www.animationfactory.com/
You can go to the Tools menu at the top of their site and also modify a GIF from them, or from your PC.
They let you upload, but only GIFs, no JPGs.
You can also use the menu once on the Tools page to make your GIF into a transparent one like my avatar to the left.
I got it from the above site a few years back.
You will notice there is no colored background like some you see, it's transparent.