I do 3D modeling (I hope that counts?). Right now I think my favorite is a a spacecraft I completed not too long ago, but the reality is that each one I produce is a learning experience. I've gotten better at making things look detailed, learning how to texture, and so on.
So something like the Caracal Heavy Anti-Air Gun, which is a few years old now, I sometimes look at it and see where I would do much better if I were to try to go back and do it now - but also where I was figuring out how to make things work (e.g., making the stabilizing feet actually work).
Those are some spectacular sky shots! Like, all of these are good, but those really stand out to me as impressive.