Bob, a lot of the min/max depends entirely upon their care. Max size for a lot is as big as you will allow them to get. Terrariums are pretty much the ideal conditions for plant growth - warm, moist, and lots of good light. I do have a category setup for plants that stay smaller and/or are low growing: Small and/or Low Growing - Plants By Type - Products
I will work on adding sizes to more of the descriptions though. If you are looking for something in particular now, please feel free to PM me or email (firstname.lastname@example.org) and I would be more than glad to assist you in picking out plants to fit your needs.