I think a lot has to do with your play style. Think about the kind of scenes that you enjoy or perhaps activities you'd like to try. High ceilings immediately bring suspension to mind.....having lots of space would allow for building an isolation cell if extended captivity is your thing.
Play parties would benefit from changing areas with clothing storage and bathroom facilities that can handle numbers and are easily cleaned.
Just like a house the intended use should drive design. Make a list of "must haves", "would be nice to haves" and "don't really need " or "probably wouldn't use/not my kink" then compare that against your capabilities and budget.
