I have that cage as well. Thats the one the SPCA gave me as a gift for all the rescues I have helped them with. It is a large tall space to decorate.
Only negative I have is the base seems a bit flimsy and the legs that stem to the wheels aren't super stable. We had to reinforce them with wood blocks.
The base hasn't given me any problems yet (cracks, giving out) just always feel I have to be delicate with it.
As far as decorations I have added hammocks (3), 2 basket houses similar to what you have there, a spudnik, hanging toys and bird ropes. Added an extra half ledge we made from plexiglass wrapped in fleece. A second water bottle, and a hidey on the bottom (igloo style).
Some baby rings and a rope latter across it to add more climbing options.
Its not a bad cage, big doors, large side doors for easy deco and cleaning access, wire spacing allows for smaller babies.
The skies the limit.
Sometimes I will hang a Kleenex box or tp roll at watch them decorate!