Quick link to all the Xweetok colors:
http://neocolours.me.uk/viewpet.php?col ... happy+male
Halloween and Darigan come immediately to mind.
Darigan would take some customization in order to match. The default eyes are awful. But most of the contacts look like they should help (though I don't entirely trust Dress to Impress and things like weird contacts, so it may be worth looking into before spending money on the brush).
The Pure White ones look cool for instance and match the pupil-less-ness of the others.
Very Gargoyle like to match the rest.
I think Elderly could easily be made to be zombie like. Tyrannian could be interesting too, though bolder colors than the rest (maybe put a rolling fog type item on, to dull the colors?) The expression on Ghost is better than most xweetoks, and that part is hard to change via customization, so I'm kinda fond of that idea as well.
I keep wanting to do a White Witch Doctor pet, I think the Christmas Xweetok could pull it off if you worked on the customization:
Five Minutes with DTI:
http://impress.openneo.net/outfits/1027718