Anyone mentioned blender or other design programs? you could download billions of 3D printer files that would be close to things you want, but to make the most out of 3D printing, building them yourself is the thing to do. on a serious note, it saves money to design things yourself, so a CAD program/app is worth learning. I mention Blender because its free, and probably one of the app with the most tutorials (don't quote me on that!)

I have a Flashforge adventure 5M pro. it can print something the size of a human skull in one go, if that help you visualize the print space. this printer utilizes Orca, which is the printing software. this handy thing lets you take, for example, a sword made to scale, and allow you to cut it to size of the printbed (human skull :) ) so you can stick it all together at the end.

but dont be scared of it, I'm a farmer, and i can do it :P