Actually, you can use thumbnails for images with licenses that allow for it. Fair use is just another name of using a copyrighted work under a strict and narrowly defined way ... you can ONLY use it to illustrate the object. Even if you had uploaded it, the image is still copyrighted. Any usage of it outside the strict fair use criteria isn't allowed, and so, user pages/subpages cannot have fair use images (see #8 on the criteria page). Hope this helps.