Photos app in Build 10149, how do I make gray tiles become pictures?

[Windows Central Question]

Photos app in Build 10149

If I open Photos app, instead of real picture in squares, how it should be, I see gray tiles. When I tap on them, I see a photo, but if I want to change my start screen picture, I don't know which picture should choose, because I just see gray squares.
So, I want to know how to make those gray tiles become pictures.

 

[Aldighievski]

Same thing here, but its only happening on whatsapp