I agree with Khris, strobe lighting affects certain people, as well as annoying normal eyes, so a warning MUST be given before the game starts that it contains some strobe lighting effects.
Use 2 backgrounds for the effect. One background (main) is normal and the other background (import new background) dark so it animates like a strobe. No need to use gamma settings this way.
The room will 'strobe' until you set background frame to 0.
Apart from that....