Since it's already cut off, I think I would go with some sort of an antler plaque for now. There's a lot of them out there besides the basic felt ones. I suppose you could do one of the fake euro kits (fake skull). There is a fake shoulder mount product called Budget Buck (no affiliation to this) that is colored to look like a real shoulder mount, and you just mount your antlers.
With the painted form, are you thinking adding eyes and ears, or just the basic form? I guess you would have the form already for later mounting if you went this route. But then you would have to find a cape to fit that form, instead of a form to fit whatever cape you went with later (assuming you would do that later).
Sometimes I like euros and sometimes I don't. May just depend on the rack and what else is with it.