The NPC’s were removed due to a lag issue, although it’s only temporary. Put screenshots of your skins up in this post. That will make it way easier for one of the admins to decide if they want to use any of them.
Sorry to say this but it’s not currently possible in Minecraft to emulate a skin server-side. As much as I’d love to use these, the only way to do this is to actually name the NPC an account that already exists with a skin which the client then grabs - thus we were able to have Notch (skinned with a cape) in bigcity.
Like I said before, it’s not possible server-side. The client downloads the skin from minecraft.net for the person’s name it sees. For instance, you can’t have an NPC called “MrCrazy” with Notch’s skin unless an actual (bought) account exists called “MrCrazy” and happens to have Notch’s skin.