My skill in 3D is too low to evaluate it.
highly technical , i think you should ask this in stack overflow…
When I messed around with it I had 1k vertices (maybe it was higher can’t remember) before fps suffered. There are probably a ton of factors at play though.
I would say the least polygons you possible can and still achieve the desired effect. It depends a lot if your are using an orthographic projection to make 2D stuff, or a illuminated 3D scene. The use of shaders vs fixed pipeline also affects a lot. Users above all value battery efficiency in a live wallpaper, nobody really likes to run out of battery for some eye candy.
You want to say that no one will download 3d livewallpaper?
Of course people will download it, there are lots of success examples. You just need to make it as efficient as possible, or low ratings will rain down on you.