Hi welcome to the FG community forum!
In terms of 3D models, you can check the world map with the FG database models positions:
viewtopic.php?f=5&t=34397 . Not many models in Australia, indeed. The most covered area is Europe, by far.
About textures, I have no idea how to check them. But I know that sometimes you can silly things like grass in Antartica. The solution for these is (possibly) to change randerer, like ALS or ranbrandt (or something like that).
ps: The db can be found in
https://scenery.flightgear.org/ .