Chip,
C'mon, you can do better than this..... A diorama or vignette should be based on a "vision" you have...not something that has been "sketched" by someone else. Sure other people's ideas can help big time, but YOU have to build it.... Go to a library, roam the internet until you find a picture or a story that is special to you. From that point on, you can advance in your research.
If you have no ideas at this stage, just add the tank and the figures to a simple display base and put it aside until a good idea comes up..... You should have "a vision" on what to make before you start something.... if not..... it fails most of the time due to lack of inspiration.
Be creative !