Note:

If you want to create a new page for developers, you should create it on the Moodle Developer Resource site.

Talk:Using images in a theme

From MoodleDocs

Just had a quick browse through this, I have not tested this but are there file extensions missing in the examples?

e.g. - body {background-image:url(gradient);}

shouldn't this read - body {background-image:url(gradient.png);}