I think pretty much any household glue would work. Here's a video tutorial that might be helpful
Try 3 in 1 glue or E6000. Another possibility is Mod Podge.
Hello. I have used mod podge to apply photographs the ornaments that’s one option. Using a spray adhesive might be easier. It depends if you want a protective coating over the photograph or not.
If it is a regular developed photo use a thin layer of clear kids glue , you might even use a glue stick ! I would definitely try a sample on a photo that you don't plan on using as a test, to make sure the glue doesn't show through or affect the photo !
Use a spray adhesive made for photo mounting. Make sure to cover all surfaces before spraying and ventilate the room.
In the video Craft Invaders provided they are using a glue stick not household glue. This would make the photos removable. For something more permanent Locktite Super 77 spray glue would work.
A good adhesive spray!
$-600 spray adhesive would work well, just don't use if you think you might ever want to remove the photos.
Decoupage is the technique here is a post https://www.ehow.com/how_12103438_decoupage-vinyl.html
I would try decoupage
Mod podge works great.
I think Mod Podge would be the way to go also