Alrighty, I've spent some time processing the comments thus far and made some adjustments.
1-- I skewed the left wall more so it looks like it's an odd-shaped room on purpose instead of an accident of perspective.
2-- I added a flying monkey. I feel like this sort of balances the table being in the lower third of the image and draws attention to the cavernous height. I'm not sure I'm ready to put in the White Rabbit or a the henchman Dwarf--I'm already biting off a HUGE endeavor for me. Unless it feels like they really need to be there. And you'll have to tell me if you think they should. These compatriot baddies seemed more in keeping than individual familiars that I'd have to invent.
3-- I gave them some small bit of action at the table--a toast. That felt like they were actually doing a little something instead of just sitting and posing for a group portrait.
4-- I lowered the Wicked Witch of the West and the Queen of Hearts so they look like they could feasibly get their legs under the table.
5-- I adjusted the mirror, facial expressions, some stuff on the table, & generally cleaned things up a smidge.
Thoughts?