Yes it's a conspiricy
Wincustomize is attempting to take over the world by saying there is 400 more wallpapers than there really is.
But you've got to keep it quiet, because most people aren't supposed to know. I'm only telling you this because you seem like a person that is really paranoid and no one will actually believe.
The wallpaper section is the largest on this website, and as wallpapers get added, some of them (on the last few pages) get deleted to save space.
The same thing happens in the WindowBlinds section. I was looking through that the other day, and the last 2 pages of skins were full of skins from 1999 (I think there was 1 or 2 from 98, I can't remember). Out of curiosity, I downloaded one of these skins, and it didn't even work with WB 3.4 .
Since there is no reason to keep them there, they get shifted off the server.
Well that's my theory anyway. You'll have to ask Frogboy or T-Man (or some other admins) to tell for sure, but what I said is probably what really happens.
Of course, it's more interesting to think that they're trying to take over the world, but since saying that there is more wallpapers than there is dosen't really have anything to do with it, that idea has no creditibility (sp?

).