Is it okay to tell my boyfriend he's shallow?
Why do you think he is shallow?
He posted a weird profile picture on social media.
If you think that what he posted was shallow or inappropriate, then I think it's fine that you tell him. It's good to be honest in a relationship, especially if your partner has done something to upset you.
What if I tell him that?
If you tell him that, then hopefully he listens to you and stops posting inappropriate things. It's possible that he doesn't realize that what he posted wasn't good, and you might be helping him out by letting him know.