Scans from artbooks, high quality fan art or any piece of artwork found via google that meets the requirements of the site and fits the personal tase of the cover artist. There are a lot of websites that specialize in one aspect of gaming, like sites that have all sorts of info and art for RPGs or Beat 'em ups, to name the most popular genres for that kind of thing. Some of our most talented artists even use artwork (e.g. wallpapers) found on the net and partly recreate that artwork for their personal nterpretaion of the cover.