Should I add stock images?
Does it benefit your user?
Use custom photography where and whenever possible. Authenticity is key.
Have a look at this study here by the Neilson Norman Group. It shows how often people were likely to view stock images of TVs on Amazon’s website vs high-quality photos of bookcases for Pottery Barn. When all the data was in, it showed original pics outnumbered the stock imagery results.
The study also showed that users gloss over or entirely ignore generic or stock images. It showed pictures of real people or products in a realistic setting gained much more attention.