My boyfriend looks at stock photography for a book he is writing for character inspiration.

Yes, for real.
Sometimes when I'm having writers block I'll look at photography or read other books in hopes of inspiring myself.

I would need more detail to answer this question...like what kind of stock photography is he "researching"?, and what kind of book is he planning to write?

imagine that having other focuses for inspiration.

What kind of book is he writing?

For real for sure.

For real, stock images are typically of relatively modestly dressed women anyway

I've been researching for near 18months now for a novel I hope to start next January. I too delve into stock photo's of women and female children from the Georgian, Regency and parts of the Victorian periods. This is to cover the lower, middle and upper classes in society. Even Jayne Austin and Emily Bronte don't go into detail. I also check for modes of transport and food. I am also checking out fetishes of same periods. But even if he is checking out porn it will be a learning curves anyway.

For real I think.

If it's just stock photos that's nothing. You catch him looking at porn then He's full of it