Boyfriend has no fashion sense.. GUYS, how to approach this topic?

I've been dating my boyfriend for a few months. Things are going really well, but sometimes his poor taste in clothing bothers me. I find many things about his appearance attractive, just not his clothes. For example, he wears high socks with shorts, shirts & sweatshirts that are much too big, or shirts that look really old.

I haven't brought this up to him, because I don't want to offend him. I think he would look a lot better if he wore stuff that fit better. Is it mean to talk to him about this, like would it seem like I am trying to change him? Any suggestions on how to bring this up?
Boyfriend has no fashion sense.. GUYS, how to approach this topic?
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