Sigh-Fi

If it's a tetrahedron you're looking for, you'll want the Goa'uld of Stargate 😁

The Borg Queen ship gets kinda close as it's diamond shaped.

Buy yeah I get what you mean. I presume a cube or really any of their geometric shapes, were picked just because it's so contrasting to anything we'd expect (not lore wise, like production wise). It's not streamlined at all (like the classic saucer ships) nor aerodynamic (granted in space doesn't make sense, other than maybe to keep the deflector shield small, but probably done because it just looked good). Try to make them as alien as possible, even when contrasted from like the Kingons, Romulans, Cardassians, etc.