Leslie Hamer created some awesome banners for her shop using Aviary's image editor. Excerpted from her blog with permission:
Customize any of these Etsy banners with your shop name and info quickly and easily using Aviary in four simple steps:
1. Click the "Customize this banner"; link under the banner you liked to launch Aviary.
2. Select the text you wanted to edit in its layer on the right, and use the text tool (the letter A icon in the left hand toolbar) to type your new text. You can also edit fonts and change the text colors if you please.
3. Select ‘File < Export Image’ and follow the steps to save the image to your desktop.
4. Then, on Etsy go to "Your Etsy" and then "Appearance." Upload your newly created banner for all the world to see!
Want to make your own etsy banner using Aviary? Follow this handy tutorial.