some Gundabad ideas:
Wargs (no riders)
Half-Trolls
Wolf Riders
spellbook pwers to fill the two empty spaces:
summon Azog the Defiler
info note below: "So you think his defiling days are done, do you?"
summon Goblin-Town Goblins
info note below: summon 3 hordes of the goblins of Goblin-town Goblins.
a couple Buildings:
cave-guardhouse
(arrow tower; texture could be a hollowed rock with slits for archers)
ideas for maps to include:
Mount Gundabad
High Pass
Goblin-Tunnels of Moria
Caradhras
hope i helped.