Wow that's amazing! A fantastic cage/habitat
Agree with Cypher about the hanging toy but the shelf looks ok to me - if he jumps off he can land on nice soft substrate. Open ladders/ropes can lead to hammies getting tangled or feet caught up or other injuries. It's not too high up but might be better with something else instead. Just a safety thing. Maybe a large tube/tunnel leading up there? I like the cork logs.