I like them. They may be more incentive for me to play some ZM. Since, at the moment, i don't play ZM.. id like to see some sort of skins integrated into other servers, as well!
Like:
http://cscz.gamebanana.com/skins/106338
http://css.gamebanana.com/skins/109799
(even if for admins/ula/clan only)