Examples of molecules with D4 and C9 point groups
For nearly any point group which is actually feasible (including $D_4$), look up the Symmetry gallery. Your all-cis tetra-substituted cyclobutane would be $C_{4v}$, BTW. 

As for $C_{9h}$... well, I don't quite believe this is possible, but probably we may come up with something that would look almost realistic.

A substituted nanotube fragment will do, I think.


Surely it is hypothetical, so what? Cyclo-$\ce{C18}$ is hypothetical as well, and in my opinion, has lower chances to be stable. Also, its symmetry is kinda dubious.