Get some string – very cheap in Deals shops. Take a puncher, and some pegs, some double sided sticker tape, and your favourite pictures, photos etc.
Here I have a penguin – my favourite animal. Just punch a hole in the head of the penguin and pass him through the string. Use pegs to hold up any image/items you don’t want to punch a hole through. Adhere to wall with sticker tape.
It’s a simple product and you can add it at anytime.