Disclaimer: The tiles might fall off after a while, especially if it is a shelf/shelf with something on it or the wall is hit from the back.

This is a modular tile system that I designed to be attached onto existing walls. It was inspired by the Portal/Portal 2 panels. Print as many of "wall tile back v2.stl" as you need to cover your wall. These are screwed into your existing wall using 4mm screws. The other wall tile files are the pieces that can be swapped. They are all designed to print with their backs on the bed, so you need to print four claw pieces for each wall tile and snap them in to the slots on the back. They are a bit hard to push in. The grippier claw piece has sharper "fingers", which makes it harder to pull off the wall tile back. It is recommended to use the grippier claw pieces with a heavier tile or if heavy things are going to be put onto a shelf. An allen wrench works best to pull off tiles that you can't get your fingers behind. Also, the wall tile back piece is a slightly bigger than the front wall tile pieces. This lets one screw them in right next to each other and still get an allen wrench behind the front piece.

Feel free to make your own tiles. I included a blank tile for this purpose. If you want to resize the tiles, I recommend not scaling it all down as one, only drag the corners of the tile in or out. I'm not sure that the claw pieces will snap in normally if their size is changed.

Edit: I replaced "wall tile back.stl" with "wall tile back v2.stl" The v2 allows for heavier things to be placed on the shelves.