I don't, although I want to say someone posted a photo once.

If I recall, it's underneath the central B complex somewhere. The only doors go outside to the apron, where the bus lanes run. It is separated by a border post into two rooms and each half has a door outside. Last time I used it, I had a 0h55 connection LAX-FRA-VIE and we were arriving C, so I was grateful they took us down the stairs to a bus and straight to the A gate for the VIE flight (after entering Schengen).

I'm probably wrong, but I want to say it's in the vicinity of the BSO/BSW bus gates, but not marked on the airport map. The inside of the checkpoint office might have a door going into the main airport, but nothing for pax.