Use lo-res figures where you can in the mid or background, I've found the V3 and M3 RR figures particularly useful for this. I'll have my main characters using the full V3, M3 whatever in the front of the scene and then the RR figures in mid or back!

OR

You might want to look at using the AZL crowd kit, that's pretty useful for background peoples or so I'm told, I dont't have it but it has been on my wishlist!

Injustice will be avenged.
Cofiwch Dryweryn.