It's quite a dimly-lit area, and I think my use of flash has made it look particularly ghastly (as well as exposing bits which would otherwise be ignored). It works though, and the Murray-Darling area is quite nice to walk through.
after I posted that I was actually thinking "I wonder how it looks in real life". I know that, for example, fake rockwork in Aquariums can often look great in person but shocking in photos with a flash. If it looks good in real life that's the main thing.
I've finally got round to reading the official guidebook - apparently this area's theming is supposed to be dream-like, and is inspired by aboriginal art.
Signage throughout the aquarium wasn't great, but I'm glad that I've finally been enlightened.