Transmog, Mount, New Gear?
Warmane did transmog system on wotlk realms. It's was awesome. But its not enough for players. Everybody loves wotlk but everybody likes new mounts, new artifact weapon appearance.
I suggest bring new mounts, weapon appearance (maybe some cool Armors) to Wotlk realms from newer expansion. (maybe hard-custom quest rewards to get items)
I know everybody will say ''its blizzlike, its not custom server''. But nobody cares blizzlike. Warmane already custom server now.
Think about: U will ride dread-raven, heart of aspect, cloud serpents, gron mounts on dalaran. It'll be so unique.