I have a few ideas, but for the being I'm going to keep going.
I added more to the auditorium/restaurant lobby including chandeliers. I think it's kind of busy, but that's me.

I also fleshed out the bump-out area in the middle of the tower.

And the new floor is ready to go.

Don't know what I'm going to do yet, though.
Edit: Also, I recommend getting rid of the floors and leaving the Internal Design until the end. I think what we want to go with First is a Shell so your Turtle isn't Exposed. Or else the Windows will Screw with them, as will mostly everything outside, so what you want to do is save the Easiest for last.
I thought about doing this, but it is so hard to come back and put floors in. It's easier to incorporate the floors and some of the interior as I go up, plus it gives me a better sense of accomplishment.