Method 1: the area of hanging tapestry probably meets your requirements, with a little color element. Nail the photo frame on it, or paste the photo directly (or use double-sided tape and adhesive tape). )

Method 2: Use wooden strips as the background wall (similar to the chairs in the park), and then hang the photos on the background wall. It looks better this way. You can hang other things.

Method 3: Clean the wall flat, stick it on the wall with some small hooks with glue on the back, and buy a photo frame that can be hung.

Method 4: Plastic seal the photo and stick it on a wallpaper with double-sided tape.