I'm wagering it's already been suggested in one form or another, but my humble suggestion would be to soften or remove the coded class/race enforcement that currently exists. To clarify, I am not advocating a classless system, but one where classes are not bound to specific races. For example, combinations that are not currently possible-- Undead Paladins, Gnome Priests, Warlock Draenei, etc, etc. Though it would break lore to a degree, I believe this (hopefully) simply alteration would add beneficial flavor to the Icecrown distro without breaking the game, perhaps even enhancing the experience.
The only hard challenge I see to this suggestion besides coding would be training NPC placement. You could leave things the way they are (it's not exactly hard to travel to the appropriate class friendly zone) or drop in a few low level NPCs for convenience sake.
With an eye toward revenue, Warmane could make this a donation bonus, similar to unlocking DKs and allowing que priority. Donate ___ and unlock all classes across all races, for example. Though it may just be me, I'd wager you'd see an uptick in donations just for this lifestyle perk alone. In the end, it's not all that outlandish of a suggestion since MoP sets the precedent to a lesser degree. And those goddamn limited hairstyles, but that's a topic for a different thread :p
In either case, I'm enjoying myself on Icecrown and appreciate your efforts, Warmane staff-like people.
Custom contact is a strict no, unless there is a very good reason to consider it, and this is not one of those.
Custom... content? If that's the definition, then I'd argue that you're already offering that by unlocking DKs for donors before 50-- that is to say disassociating content from its account/level requirement ---and I'd think the revenue alone would be a good reason in the same vein...