Two other poses were tried and I emerged from the booth to find photos of me as Indiana Jones, a fireman from Backdraft and a wrestler being strangled in a headlock.
The MERL system uses 3D face models and specifically targets illumination and pose variation, which they think as the most critical factors limiting performance.
If anything, it's nice to have a couple photo poses that are flattering and you know you look good from that angle because it is really annoying when your friend wants to retake the photo like thirty times.
So before the test, you go and find a quiet place or just sit on your chair, close your eyes and start to imagine the test, you walking in, smiling sitting down, confident posture.