Almost every bike I saw was of a similar type: aluminum frames in one, maybe two sizes, step through frames, high bars, fenders.
This type had airless tires and belt drive. I think it was a rental:
Typical was a single speed, drum brakes front and rear, and this odd 24" wheel size. Maybe it's more maneuverable in the crowded city:
I also saw a lot of these orange and silver models:
Definitely a rental, there was a big electronic lock on the back:
These yellow Ofo bikes were all over:
Here's the 24" tire:
And the blue bluegogo model as well:
I also saw this faux fixie model in several spots:
And another oldie with a rear wheel stand:
I think this rear rack could support a family of four:
I wasn't brave enough to rent out. Chinese traffic is crazy enough that crossing the street while walking was scary enough for me!