I think you scored fairly well with this pic, although I'm sure you would have liked a slightly higher score.
I believe this is a very good Self Portrait, so well done. The lighting is very well done, which creates a good atmosphere. Somebody commented about the chair back being distracting, and I have to say I tend to agree to some extent as it is only really visible on one side of the frame. This is only a minor nitpick though and I don't think had a huge impact on your score.
I am not really sure what you could have done differently to secure a higher placing/score. Perhaps it just doesn't have enough of the WOW factor needed to win on DPC.