I know this is old, and you've probably made some decisions and done some experiments since your OP, but here's what I'd do.
I'm not a professional woodworker by any means, so please grab some salt, but if there's something you want to make and sell, do just what you did with the bowtie shelf: make one, list it, respond to orders. Just be realistic and upfront with your customers about how long it's going to take to deliver before they pay you.
You can do whatever you want, keep making bowtie shelves as long as people are asking for them. As long as you're not stockpiling things you don't already have orders for, I wouldn't even think about saturation. Most semi-professional craftspeople I've seen stumble when they start asking too many questions rather than just making and selling things.
As far as IP law, that's another question that I wouldn't even ask. The worst thing that's going to happen is you get a C&D letter, then you just C&D and find something else to make. Unless you start making TONS of money, or start building trucks and motorcycles.
Anyway that's just my two cents. Make whatever you want, and if people want to pay you for it, make some for them too.