I always thought that the one thing really missing from spacedock was a massive ship docked outside....like a galaxy for instance. It wouldnt even have to be something I could explore, just a huge ship to fill up the windows as I walk by.
Flying around in the ships tends to remove some of the awe from the sheer size of the ships. This would restore that IMO.
Actually it wouldn't be that hard. There was a Star Trek roleplay sim in Second Life, where they were building a 1:1 scale (interior and exterior) re-fit Consitution class (covering two sims). The detail was pretty good to.