Back before the WotC minis came out, I used a variety of those glass counters you see at a lot of craft stores. Need 20 kobolds? Use 20 green counters, and throw in a couple reds for spellcasters, and maybe a blue one for a boss kobold.
Because I needed to be portable (we gamed at a friend's house), I used a medium-sized clear tackle-box to hold all my dice and counters. I had no trouble representing everything I needed with about 4 different colors.
Another option is to buy minis bases, and get different colored stickers. Make about 20 of one color, 20 of another, and then maybe 10 each of two more colors. And don't forget to get bases for large-sized creatures too. Be sure to number them to help tell them apart, and track injuries, death, etc.
By not using specific pics on the counters, you get to recycle them, and that means less clutter, and sorting of all the different types of monsters you would normally have to have different counters for.