Document background image feature

about.md

@@ -18,6 +18,7 @@ They say three times the charm, so here is another free responsive Jekyll theme
 * Gracefully degrads in older browsers. Compatible with Internet Explorer 8+ and all modern browsers.  
 * Modern and minimal design.
 * Sweet animated menu.
+* Background image support.
 * Readable typography to make your words shine.
 * Support for large images to call out your favorite posts.
 * Comments powered by [Disqus](http://disqus.com) if you choose to enable.

theme-setup.md

@@ -165,6 +165,19 @@ links:
     external: true 
 {% endhighlight %}
 
+#### Background Images
+
+To utilize this "feature" just add the following YAML to a post's front matter. ([View demo](http://mmistakes.github.io/hpstr-jekyll-theme/background-image/))
+
+{% highlight yaml %}
+image:
+  background: filename.png
+{% endhighlight %}
+
+This little bit of YAML makes the assumption that your background image asset is in the `/images` folder. If you place it somewhere else or are hotlinking from the web, just include the full http(s):// URL. Either way you should have a background image that is tiled.
+
+If you want to set a background image for the entire site just add `background: filename.png` to your `_config.yml` and BOOM --- background images on every page!
+
 #### Other Stuff
 
 The rest is just your average Jekyll config settings. Nothing too crazy here...