adCenter is rolling out a pilot program in US to test image ads for their Content Network, including MSN sites. Image Ads can be purchased on a CPC or a CPM-basis. To participate, you must own IAB Standard creative and tags. Then follow:

1. If you manage your account on your own, then call the 1-800-518-5689 support line and ask to be enrolled into Performance Improvement program and the Image Ads Pilot.
2. If you are in a Managed Service program, you should ask your Account rep about the Image Ads pilot