I agree. Brianna Love has a fantastic ass, and I would thoroughly enjoy plugging my nose up her butthole. There are many videos on the internet which show her sitting on a guy's face, but I'm not aware of any specific "facesitting only" videos.
Both of these videos show her sitting on a guy's face:
Go to minute 14:00 in this next video. She smothers some guy for a few minutes, and talks about how the guy can't breathe under her ass:
And lastly, here's a good video of her ass, as she walks away from the camera. It doesn't have any facesitting, but you'll love her ass:
Hope this helps a little...