He has a very limited vocabulary.

He needs to expand his vocabulary?

Wow usually would mean he likes what he sees?

:o

Time to put your clothes back on?

Wow is a vague expression of amazement. He could mean "Wow you look fantastic" or "Wow will you please stop"

he lacks imagination?

Also means you are trying to tell us how good you look

You’re probably sending too many selfies 😉

he's impressed by what he sees.

You could make him speechless with your hotness or maybe just indiffrent or ordinary. You shoulda included a selfy for an accurate answer or poll

Wow.

Try a different guy

He's at a loss for words?

he lacks vocabulary skills

He likes nude selfies?

Maybe he really is attracted you. Or he's really horny, or both.