Function of が instead of な here


あなたのへんがお写真を、シアトル市におくります。 What is the function of が here? why not あなたのへんなお写真？




This is a context sentence from WaniKani, right? They don't use kanji in the
sentences if you haven't learned them yet.

へんがお is 変顔 "funny face", like the kind you make when fooling around.

