Just saw this as I didn't vote. I find it an interesting interpretation of Avedon's style. And I do see how his Beatles "popart" could have inspired you to this. Pretty good - better than what your score implies.
Technical: Composition is very strong, the fill the frame of your subject works very well here. As a posterization, it appears to be done well, but I don't have a lot of experience in that area, posterization being something I normally try to avoid.
Aesthetic: Overal, I think this works well. However, as I look at it for an extended period of time, I find the abrupt change of colors distracting--as they create their own lines. I wonder how it would have looked with wild colors like this but smooth transitions? Maybe something to try.
Challenge: I couldn't find a similar Richard Avedon shot.
Conclusion: I think you have created something special here. It works, but I still think there might be improvements--or at least fun experiments--to do with it.