Is it only possible to select a Payment Gateway that

Is it only possible to select a Payment Gateway that isn't on the list for Marketpress and still integrate Marketpress features on my website? I am trying to get a Payment Gateway set up, but at initial signup they denied our website for some reason. Is there ANY POSSIBILITY of you adding Gateways for HIGH RISK businesses? We sell videos for online purchase, as well as clothing, eventually. I'm hoping there's a way we can integrate something that works. Please help!