Are Many Christians postmodern in their approach to modesty? Christians have a wide variety of opinions concerning modesty. Many say that if you believe you should dress a different way than that is fine for you--just don't impose your beliefs on us--because the bible doesn't explicitly define modesty. That seems to be a postmodern way of thinking. 

Being a Christian means trying to be more like Christ and incidentally less like the world. Many "Christians" seem more interested in being a close as they can to the world in how they dress. Surely that stance denies the truth that we are to follow Christ as best we can and is therefore "postmodern": If we aren't supposed to follow Christ as best we can, does truth even exist?
With all due respect, to compile the entire Christian community into a composite entity and then direct the question at that entity is at best unfair. To be a Christian certainly involves always being cognizant of the image that one is projecting to others in their daily life, and to that end a Postmodern stance on one's level of modesty is contrary to the teachings of Christ. Do some Christians reflect a Postmodern preference of modesty? Of course. Do some Christians consciously value humility instead? Most definitely. It's no different for any other religion. This really comes down to a case-by-case basis and can't be applied to the Christian collective.