I would have thought that the amount of live rock you have in there at the moment would be sufficient to support the bioload of a suggested stocking list for a tank your size. You could add more live rock, purely for aesthetic reasons. If that's the only reason, then you could get a 25kg bag of ocean rock from your LFS and add that to the tank.
You can either use this as base rock and stack the live rock on top of it, or mix it in with the live rock as I have done. Its pretty stark white in coloour to begin with but, mine has already greened/browned/redded up a lot, where algae has moved and the snails graze upon it, as well as the hermits. It will also become live in time. Although not as porous live rock, it will still house the bacteria and do the same job.
Well worth considering, as I think your next step before you add any fish, corals or cuc's, will be to aquascape your tank.