In your Android browser (stock) click on a image. This will display a larger version of the image. Long press on this image and select save. The image will be downloaded to the download folder on your device. To pick the image as your background, click the Select Background button and select Gallery. In the Gallery look for a folder Downloads or My Downloads. Here you will find the image you’ve downloaded. Simply select it and voila, the image will be set as your new background.
Tip: you can change the background in any theme. How a background is displayed is depending on the theme. The best way to start with custom backgrounds is with one of the Plain themes.
Feel free to share your backgrounds! Mail them to firstname.lastname@example.org and they will be put up here (with the name of the author if you wish)
General (Tablet optimized but with some scaling exceptions will also work on the phone)
Here templates will be published for tablets and phones. With these templates users can create optimized backgrounds for the keyboard. (Coming Soon)