The graident is actually a background image as well. Luckily you can, in modern browsers, have multiple background images.
Example:
background-image: url('http://www.w3schools.com/cssref/smiley.gif'), linear-gradient(to bottom, #FF9100, #FA6800);
And you also need to do the same for the vendor specific gradients.
See this link for compatibility table: background-image MDN