making backgrounds
One of the hard things about making banners is getting a background. Of course, you can always just use an image for a background. There are other techniques, as well. Here's a guide to help you make great backgrounds using GIMP!Gradients
The easies background to use, aside from a solid color, is a gradient. First, choose the two colors to fade between. Make one your foreground color, and one your background color. Then, edit the type of gradient your using in the gradient tab. If you don't have the gradient tab, add it by clicking on the following image then going to Add Tab >> Gradients:


Patterns
While these aren't the best backgrounds, these can be played with. You can also use your own pattern (you can download them yourself, or save them as .pat and install them using the same methods as brushes but in the pattern folder) First, set the pour tool to Fill Type: Pattern Fill (under tool options in the tool tab) Then, just fill the background with one of the patterns. I'll use the stone pattern:


Images
A third way to make a cool background is to use an image. So, the first step is to Google search (or use one of your own pictures) for an image to use in the background. Be sure you aren't breaking any copyrights, such as using hand drawn images, photos, or any other pictures that are copyright to someone. Check the Terms of Use if you're not sure. I chose to use a picture of trees for my background:


Closing
As you can see, there are many ways to make cool backgrounds in GIMP. You can also use cool brushes that you download, or find your own creative method. Just remember to try everything, and you'll find a sure fire way to make backgrounds you love. :]