Off the top of my head:
- A wedge shape (slope)
- A prism shape (OK, that’s just two slopes end on end). Good for roofs.
- Arch.
- Corkscrew
- A flag
- Cogs
- Maybe some platonic solids: tetrahedron, dodecahedron, etc.
- A torus
- A vase shape that follows a curve.
- Pipes
(OK. None of these are strictly necessary. But what’s the harm in having them? Better too many than too few! Like who actually is going to use a spiral staircase? )
BTW your videos give the impression that you are able to sculpt the level inside the game engine? I didn’t realise that you are expected to use an external 3D creator. It’s kind of confusing about what is the expected workflow since it is possible to edit geometry in the editor. Unlike, say, Unity which has no geometry editing so you know you’re supposed to create the geometry outside. This might be more obvious to big game studios but not so obvious to beginners.