My master and I have a tiny place, and we just use whatever room and furniture is handy. Chairs, desks, and tables that you already have can work great. You can experiment and see what furniture works the best.

I think that the best playrooms develop organically as the couple or person figures out what is needed and what would be nice. Maybe start out experimenting with what you have, and then acquire BDSM specific furniture as it is needed, for example if it turns out you don't have anything that's the right height for spanking over, or you want to tie a person up in a certain way but there's nothing that works well for that.