Thats why I put in the "Notes" field for adding ingredients. I was going to put a checkbox for "modded", but I figured a text box would allow for more flexibility (ie. some people say "recolored"). I noticed no one is really using that feature though. Is it unclear? I guess I should put in a tip below the field saying to note if it is a mod.
Also, since mods are so common these days, we have been talking about trying to support a movement to making skins more "open" so more people allow their works to be have ports/mods *and then* they can be uploaded with proper credit. There is an option when you upload to identify the original source of the work, so credit will be given and works will be networked (like screenshot ingredients).