All the ones I've visited do not allow them. Going from google adsense (if this is accurate, if it's not please tell me where I can find accurate) I've received 15,910 impressions so far this month. Last month I received 65,111 impressions. I know I can increase these by adding to another area, and I've been well within the needed impressions. This is a virtual petsite, and we're constantly adding things to it. Which I feel will be enough to maintain, if not increase the amount of impressions. Any help with any of this would be appreciated, thank you
Here are some cpm ad network that might accept your site, but not sure on 100%, so you would have to try them and see. AdBrite, Cpx Interactive, or Snoork Ads.