I really like the concept for the floor and the way it has been drawn makes it feel like the central dais is floating in space. The blue marble is very rich looking as well. As for ideas on what to put in...well, I'm more of a big picture guy and leave the details to those more suited for the task but I'd put in a bunch of moons floating around the edges so that they could display lunar phases with orbit paths and one could stand on the dais and contemplate the moon. The I'd put in 4 arched bridges at the compass points to add to the sense of "falling into space". Some constellations as well. I'm sure some other stuff will hit me in time but I hope this helps for now.