I agree with this.
I work very hard on my designs and am dismayed to see these re-uploaded even when i ask them not to.
May I suggest a fix for this? Put a switch in the upload process that a creator can check whether or not they will allow a re-upload.
That way, challenges can be re-uploaded with the permission of the creator. How hard would it be for one of your programmers to do this?
In any case, the re-upload problem is serious and ruining the gallery experience for the people who really make this game fun; THE ORIGINAL CREATORS.