Assistance with CPM/CPC/CPA selections

Hello,
My company runs a photo image hosting site (similar to webshots, photobucket) that has been in beta phase for the past 13 months. We are moving towards our official release in two months and would like to get our ads situated before "going live".
We are looking to display 1-2 banner ads on each page that display ads for large known companies that pay either by CPM, CP, or CPA.
SITE INFORMATION:
Approx 8,700 community members
60% of users are 15-25 years of age
55% of users are women
Receive traffic from over 200 countries (top 5 are: US, UK, Spain, Italy, Brazil)
Deliver 300,000 page views per month to 12,000 unique viewers
One problem I do foresee is finding the right ad network(s) that deliver good advertisements to our top country of origin. There is no point on wasting traffic for $0.01-$0.10 eCPM.
Any ideas or directions you can point me (our company) in would […]

See original post by redcoat