What do you think of the name "Tehran" for a dog?

Wouldn't advise this. Tehran is the capital city of Iran. With all the anti-Muslim feeling going on and vice versa, this might not be advisable. It might offend someone.

no matter you call your dog tehran or assad.

As long as you like it is all that matters. I myself don't care for it all that much, but it is unique.

I think your dog should be named after some charcteristic about him. not about possibly something about the owner. there is a reason, something about you that made your parents name you what they did. if not just be happy your parents didn't think the name pig vomit was cool.