There are a couple pieces of concept artwork (one interior and one exterior) along with a few details from the Fact Sheet released by Disney. Aside from that they haven't been nearly as forthcoming with details on the Treehouses as they have with BLT.
I think it's understandable since BLT is the focus. They needed to be prepared to start selling BLT just 5 days after the announcement. The treehouse points won't be available for a while yet, so they have time to pull all of that info together.
In the meantime, I gathered as much information as I could and published it
HERE. Hope that helps answer a few questions.