In typical TRF fashion, you asked a question, so I'll answer a different one. . .
When I first got my printer, I found some good models to download as skill builders - pic attached of 2 of them. The screwball is a threaded pair of half spheres and when you do it right, they screw together well. The robot looking thing is a bunch of parts that snap-fit together to create the moveable robot. I think they were from Thingaverse, but don't recall for sure.
I did do logos for my rocket venture and my main company, but don't want to post those publicly. I'll be glad to send you the files if you want to use them for testing purposes. Not sure if you want 2D vectors to practice the stl generation process or if you want something different. Let me know and I can send them to you.