I am an engineer in my day job and I love creating things with 3D printing in my spare time. When I was starting out in 2012 I designed tools, vases, toys and other things before getting into jewelry design. I designed some Celtic Knot jewelry which was popular so I focused on that and grew it. I have done many custom jewelry designs for people. In fact, probably around 25% of my designs that you see in my shop started out that way. Some examples that started out that way are the Dragonfly necklace, Heart Celtic Knot, Mother and Child Knot and others.
I have also done a few projects for people on the Upwork web site. I designed some prototype products for customers and in some cases I signed a non-disclosure agreement. I'd have no problem signing one of those again for a project.
So while I really enjoy jewelry design, the engineering side of my brain is always looking for new ways to apply 3D printing technology. I'm interested in learning what kind of project you might have.