If you download a maxwell material (ex: http://www.maxwellrender.com/materials/material/details/199 ) and unzip it you will see the maps they’ve used included.
Maxwell has a lot of procedural textures so if you don’t see any .png or .jpg maps included in the zip file, it means they aren’t using textures they are using procedural methods. The one I linked to shows a diffuse map, displacement map, and normal map.