On the right you'll find links for various sizes of customised MRFC PC desktop backgrounds, one of which should suit the size of your computers' screen resolution.
If your not sure what your computers' screen resolution is, for Windows users right click on your current background and select "Poperties", then a window should appear. Click the "Settings" Tab and in the lower left of the window you should see "Screen resolution" with a slider underneath. On the right of this page select the size that matches your computer or the closest size to it, then download the MRFC Desktop Background to set as your new background!
If you're not sure how to set an image as a background, ask someone who does know!