^
You're able to do it yourself in your User CP. If you're having trouble getting it to work/show up properly, the fact that you're trying to use a pic that's hosted on DeviantArt might be part of the problem, since they do not like it when people host pics on their servers but hotlink them to other sites. Your best bet is to make an account for yourself on an actual image-hosting site like PhotoBucket and just rehost the GIF there. If you just try to use the one hosted on DeviantArt, it's not guaranteed that it will work/show up properly.