The background color of a Web page without any customization is white. HTML Web programming language enables you to change the background color as well as add a background image.

One way to add a background photo to any custom Tumblr theme is to embed a simple CSS tag at the right location in the theme's HTML code. Navigate to Tumblr and log in to your account.

Cick on Choose to accept the new background. If you want to add your own image as a background click on the plus sign as above, but use the Finder window that opens to locate your chosen image.