Now I know that most GMs, in practice, play the astral as being the PCs playground until they try to punch some security.
But I think of it more like a prehistoric ocean. It's mostly empty, but there are things there that are dangerous. This in part because it's pretty much unenforced and anyone can get anywhere.
Now if you could have ranged attacks in the astral things would be nuts. Such as toxic shamen just blowing away random people in the metroplex. Mind you I have that, it just isn't so easy for them.
Anyway so I've got a mix the stuff in street magic, but also:
The aformentioned eco shamen. They run the risk of going down themselves. But they mitigate it by bringing in spirits. Just to wreck a little havok in the astral with the desecrators of the planet.
Other cultures that don't like the UCAS. Some projecting religous fundamentalists (take your pick) that are pissed. So as an initiation right they have their members go into a megaplexes astral and off someone.
Also I try to recreate a little bit of the territorality of the old shamantic spirits by occasionally having spirits be attacked if they're inside what I would consider a hostile domain. A fire spirit on a ship, for example, might get hit out of the blue by a water spirit. A spirit of man inside a woods might get smacked by a spirit of beasts.
And occasionally a powerful something will attempt to boss an astral traveler around. For example a dragon/free spirit might appear to someone in astral from, inform them they know where their body is, and basically reverse the whole services thing. Giving them a task to do.
And of course there are dual critters if you aren't paying attention or are manuvering in the sewers or something.
Still some variety would be good. Ideally stuff that seems realistic and might be interesting. An astral aquatic dinosaur would actually be great if there was a reasonable excuse for something like that.