Hmmm...indoors and in a tiny space...that's a difficult one. Like pattoncommander said, I would recommend outside so that you get more manuever room. But to answer your question, 1:24 is about as big as you can go. To the best of my knowledge, that limits your options to VsTank'sTiger I. They plan to release a Sherman, but it's not out yet.
VsTank does have a micro series that includes a Panther G, Tiger I, T-34/85 and a Sherman. While, I'm not keen on their looks, they might be the best way for you get more use of the small space that you have.
Here's a website:
www.vstank.com.