Good question. A bit of googling turned up this

The best angles however are obtained when you shoot more or less diagonally towards the climber from a higher viewpoint. They are obtained when doing a traversing pitch when you are climbing, but quite difficult to obtain in most cases if you are not a climber. Exceptions are places where you can get easily to the the top of the climb, such as the Verdon gorge in France, or, to some extend, Half Dome in Yosemite, CA. Even when you are climbing it is not that frequent to obtain these angles, and if you get them, you generally have to photograph a second, which is not as dramatic as photographing a leader. That's why a large number of photos published in magazines and adds are taken on rappel. You rap down, hang from a rope, and photograph from there. The perspective is generally very good. Wide angle lenses work best, since they tend to accentuate the height (distance to the ground) and the converging of natural features. Be careful not to include you own rope in the picture. It is also necessary to have a relatively fast shutter speed, since you will tend to spin. A comfy harness is appreciable. The perspective is the best if you are actually well-detached from the wall so you actually shoot from behind the climber. Overhanging routes allow you to do that naturally. Otherwise, film crews have been known to use set-up with poles to keep them away from the wall. I believe that a suspended tripod (with the feet against the wall) would work fine. When you are shooting this way, you are actually not climbing, but your point is to shoot, although you are using at least some climbing techniques (rappeling, jumaring).