Did you know that Thesis has supported adding custom background colors (but not images) to the <body> for a few versions now? Well, it has 
WordPress has decided to catch up and add in a CSS background generator. Basically, WordPress adds <style> body { background: blah blah; } </style> to your <head>.
Remember, this is completely unnecessary if you just want a background color. Thesis already provides this functionality. This tutorial is aimed towards the very lazy user [ahem...] who wants to put a background image on their <body>.
Here’s what you do: open custom_functions.php and enter the following:
add_custom_background();
Embarrassingly simple 
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