Most Helpful Guy
Him enjoying those pictures isn't something most people would consider a problem at all.
Him clicking "like" on them is slightly dissrespectful and would annoy quite a few girls but still isn't technically a breech of the typical relationship terms out there.
If it's a occational thing don't do anything about it.
If he does it a lot have a chat with him and tell him how that makes you feel.
Don't accuse him of doing anything wrong pr say, just let him know what effect it has on you then the two of you can talk about how to deal with that.
Generally speaking I'd say that feeling uncomfortable about your partners interests or activities regarding others is a symptom of a lack of faith in his love for you and in the relationship itself and something that *should* be addressed.
Not because he's technically doing something wrong with looking at or liking those pictures but because it means you don't feel loved enough and secure enough in the relationship to not care about it.
And the solution isn't neccessarily him stopping.