you don’t need to create 30 materials, just one is enough. in the blueprint you only change the texture.
if you are using textures(images) in the above solution replace color with Texture and convert to parameter.
in your blueprint you make an array of those textures(images), then get random item and set to Texture Parameter.
if you don’t want the boards to have the same material you should probably have the two boards in the same blueprint.
