I was genuinely curious & mystified as to why it's bad to depict Mohammed, here's what I found.
it's not bad at all in the Qur’an.. BUT Sunni Muslims (the majority) also follow something called hadiths, which are the next best thing after the Qur’an and in there it says. any pictures of people or animals, especially in homes is prohibited.
Ok so I'm more mystified than before, apparently if you're a devout (Sunni) Muslim, no family pics etc at home or you're in trouble.
links:
http://www.answering-islam.org/Muhammad/pictures.html