A interesting group, at another glance. The entire 'house' could be divided by the powerful-but-unpredictable Everfree forces and the generaly more reliable non-wild side troops, like the zebras and minotaurs. The additional force's list for these guys could easily go either way: manticores and such could be neat warbeasts, and there's almost unlimited things one could do with the savage aspects of the everfree (more explictly druid-like individuals who can cast spells relating to nature? warriors that wear magical wood that acts like magical, shapeshifting armor?) but one could also make a army of zebra troops that mirrors how one could make a all-ground troop Stormwing force. A basic commanding troop upgrade to the tribal warrior seems like a obvious candidate, as is the possible chance to have a potion-thrower on hand. Perhaps the "ultimate" zebra trooper would be a tribal champion that has consumed a general uberpotion before the battle, making him or her something of a glass cannon?
There's also the minotaurs, which seem to be too much fun to leave with a single unit. Perhaps a "Satyr" is one of them that directly serves the Everfree Liege, in effect making them a scaled-up version of a Wraith?