I downloaded a lovely picture three days ago for my desktop then deleted it. Autumn leaf set against old timber. Is it possible to find it?
As Tina mentioned, it may still be in your Recycle Bin and if it's not, there's a chance it could be recovered if it space hasn't been overwritten. I just wanted to add a mention for my favorite (and possibly one of the easiest to use) file recovery program, Recuva from Piriform available here: http://www.piriform.com/recuva
since this is Windows, you might be in luck. Windows doesn't delete file instantly, it only removes the 'bibliography' entry and marks the disk space occupied by this file as available. The file will stay there until it is overwritten. So unless the file was overwritten with something else, it should still be there.
The first place to go looking is the Recycle Bin on your desktop. If it's in there, it's easy to recover. Simply right-click the file and select recover from the menu. Then look for the file in its original location, i.e. wherever you last saw it or originally saved it to.
If it's no longer in the Recycle Bin (you may have emptied it), check out the answers to this question for more tools that will help you recover the file: http://www.makeuseof.com/answers/recover-file-deleted-windows/
Good luck and let us know whether you managed to recover the file!