I have mostly been interested in 25/28 mm miniatures. But when I bought All Things Zombie -Better Dead than Zed from Two Hour Wargames I also bought some 15mm Zombies and Survivors from Rebel Minis. I ended with about 40 Zeds and 5 survivors. Enough to play a smaller game.
Around the same time I ended up getting some 28mm Zeds picking up 2 of these packs from Wargames Factory. For some odd reason I gave one pack to someone I know, and kept one. Wish now I had kept both, as one pack basically gives you 24 Zeds. I have plenty of gangers and military in 28mm to sport a larger game.
The question of course is "Do I purchase more 28mm Zeds or build some terrain in 15mm scale?"