well the tower would be flying, no need for portals or anything like that, just magick the tower up and let it teleport and shift planes, need a change in scenary every so often after all.

I suppose on a more sensible non-ridiculous in cost/power note, I would include a nice museum-type area displaying all of the artifacts collected by the mage over the years placed conveniantly next to the entrance hall where guests teleport in or dock their aircraft.

A map room would also be good, with a magical map that automatically updated itself to show the inside of the tower, locations of people, and the surrounding terrain (especially important if the tower can teleport/plane shift )