There are no specific SEO tips for a wallpaper website, maybe except optimization of your images with alt description and descriptive file name of the pictures (big-indian-elephant.jpg).
Using a wallpaper script can make picture uploading and page creation easier, but pay attention at on-page optimization, such friendly url's, unique page title and description, site menu structure and so on.
Get some quality links now and then to your site, for improving rankings in search engines.
I own a few wallpaper sites but are pure html pages, no scripts. The more you add quality pages with unique text around your images, the better is the rankings and traffic.
Other than that, engage with social sites for extra traffic.