With Basic Tools found in Windows anyone can create a Texture in an Image Editor, for example Paint  using multiple copies of the "Tile" ( image above). You need to make the background Color your Grout color if you want to show it in Chief , and leave a narrow space between the copies of the Tile when you place them. Then Crop the multi-copied Image, so it will look good in Chief as it "tile's" ('cus the pun")  across a Wall. ie the texture will butt up to the last one as a "block" , so where th