If your theme doesn’t have an option to put a background, don’t worry. You can do that with HTML! Just read this tutorial carefully.

1. Ok, so first of all you need to choose the background you want. You can find WONDERFUL backgrounds here. But, if you don’t like any of these, you can also find good ones on Google. 

2. Now you have to get the DIRECT LINK of it. It should end in .jpg, .png or .gif, for example: http://i44.tinypic.com/34qjqm8.gif

3. Now find this code in your theme: background-image:url(); 
And paste the direct link between the parentheses. Click Update Preview and, if you like it, click Appearance and Save.