IF the image is embedded and defined in the CSS file, then right click it and select Inspect Element. A new developer window will open. Locate the right box and the image will appear as a URL. You can see the instructions in the image below. Click that URL which points to the image and a new browser window will open. Right click the image, choose Save As and that's it. The image will be saved where you select to.
![enter image description here](http://i.imgur.com/GlBVD8I.png)