Thank you Daruma but I didn't mean the meaning of picture. I was wondering why we say "If you aren't?" my problem is about this part of the question.
It's a shortened exclamation. (I'll be damned) if you aren't the very likeness of your Mom!
"damned" or any other adjective that suits your personality. (Well, blow me down) if you aren't the very picture of your Mom! Or any other verb (<Verb> me if you aren't ...)