You can change images on the tiles by saving a Mahjong tile using Saved Objects, and then editing the tile's .png image under Documents\My Games\Tabletop Simulator\Saves\Saved Objects. You would probably need to do this for each tile you want to change and basically recreate this workshop mod from scratch, but it is possible. More detailed explanations can probably be found online.

how can i change the images on the tiles?