This idea is kinda a free-bee.  The Crowd generators all cost a fair bit of money.  There is one on another site that charges around $15 to $50 per character.  They look awful. Animation if any is limited.  You cannot change their poses normally unless you buy the $50 one.   I slapped together this crowd of 8  TO 12 from my old G3 stock of M3 and V3'S. 

In addition for a little extra depth in the rear, I added in my old AZL flat crowd with the black silhouette chosen.

MST HDRI lighting used in a couple for additional spooky depth effect. They are watching a girl fight that has gone to the floor and from their expressions has got real nasty LOL 

The max render time for both AZL extra depth and hdri lights was 4 to 5 seconds 1280x720 .  The 8 with no lights or AZL was around 1 or 2 seconds. So hang onto your old V3 and M3 runtime.  Even now it would be smarter to buy the current stock while still available of V3 and M3.  Way cheaper and better than the low poly ones.