Extra thumbnails with red X's?

So, I don't guess it's an actual issue. It's just doesn't look appealing to me, but I don't think it causes any issues in game, as far as I can see? I like to test cc a couple of pieces a time, and that's what I was doing with a content creator's cc, the wallpaper that was in the set was just a big colorful question mark(s) on the wall so I fixed it with S4Studio. But now it's produced two new thumbnails that are listed as custom content and show up as just red X's, they're both called "simple siding" and they appear as "siding" when placed against a wall. I've been trying to figure out how to get rid of them, if possible? Or is this an issue the creator would have to address themselves? Again, they don't appear to affect anything: it's just annoying.