Customizing theme background options
You can select background images for placeholders, layouts, and content gadgets when editing them from the Site pages screen. You can also set a site background from the Colors & styles screen. When selecting a background image, you can choose from the theme-specific image library, or choose an image file from your Wild Apricot account.
The images that are available from your theme-specific image library are controlled by the HeaderBackgroundSettings.cfg file. Here's a sample HeaderBackgroundSettings.cfg file:
As you see, the file consists of links to background images. To add your own images, you can either edit this file directly, or just add your image files to the BackgroundImages folder and background image thumbnails with the same name to the BackgroundImages/thumbs folder. The recommended size for thumbnail image is 300 x 49 pixels. After theme is rebuilt, your HeaderBackgroundSettings.cfg file will be updated automatically with the new files.