Yeah however even without making any form of image of Muhammad Sunnis and Shiahs are already idolizing him anyway. So what is the point of forbidding the portraying him? Besides, in Al Quran God is the only one who can not be made an image of.

the idea that maybe one day ppl will get loss and worship these statues and images like the ppl in my story , well that's all in my opinion but i say it bcuz there isn't any picture of Mohamed (peace be upon him) and it's forbidden to show his face in any movie ..etc , i'm not sure that's the point tho

alslam alikom (peace be upon u all)
for the question "how does the kurran define idol worship"
the idols (statues , painting) are forbidden in Islam , even it was for the prophet himself , knowing that he's not the god. this bcuz how the statues worshiping starts , we all know that all humans are from Adam , Adam was a unitarian so was his children and his grand children , the kurran teaches us that Adam was a prophet himself , so they all know god and worship him , but in the next generations (all worshiping god ) there were six men very faithful and others look up to them , they appreciated them so much and when they die they decided to make statues for them so they can remember how great they were and to stay on their path , any way long after they built these statues ppl forgot what they were for , that's were the devil interfere and told them these statues are gods you fathers use to worship , then the statues worshiping starts. that's why there is no statue or painting for the prophet Mohamed.
Islam refuse statues and kurran describe ppl who worship them as (kafiroun) disbelievers ,and i mean worshiping (like saying this is my god stands there ..etc) not as a symbol like in churches , i understand they don't worship the statues itself this is another thing.
and about the main question how can a Muslim marry a christen ,(i think) that it's allowed for a man to marry from ppl of the book (christens and jews) without classifying whether they were unitarians or not , as a prove of that when the Kurran describe the christens believes about jesus (eisa) being the god or the son of god the kurran refer to them as christens (ppl of the book) so they are included not just unitarians (again that's my opinion i'm not qualified to judge in this , ask a (mufte) there are many sites and many islamic center u can ask in if u really want the answer)
at the end i must say sorry i wrote too much , that's bcuz my English is really bad ;D i hope u understand what i mean
thank u for ur time
peace be upon u all