I love it. I've always liked these above ground ponds. That's a really good example of how small can be very cool.
I would assume it's about 12 inches deep? You probably good grow a Helvola or tetragona water lily. These are minis and very, very nice. I also think that some of the small blue/purple tropicals might work. Daubin comes to mind.
Now you need a catfish in there.