Probably already suggested, but Vanguard flag and the Vanguard wall symbol would be nice.
A larger supergroup emblem, maybe twice the size of the floor plates 1-4. One without any background.
Lighter tech coloured flooring. At present we only have dark-coloured Ledge Block and Platform Floors. Some matching the basic base floor designs would be great (would it be possible to pull the graphic being applied to the base floors/walls/ceilings and apply them automatically to some new floor/wall/ceiling objects, so multiple designs would be available on a smaller number of objects?)