See The Live Demo And Feel Free To Use It!
Use Natural Earth 10m-admin-0-countries layer and the following cartocss in Tilemill:
Map {
background-image: url("images/white.jpg");
}
#countries{
[MAP_COLOR = 1 ]{ polygon-pattern-file: url("images/gray.jpg");}
[MAP_COLOR = 2 ]{ polygon-pattern-file: url("images/mix2.jpg");}
[MAP_COLOR = 3 ]{ polygon-pattern-file: url("images/brown.jpg");}
[MAP_COLOR = 4 ]{ polygon-pattern-file: url("images/black.jpg");}
[MAP_COLOR = 5 ]{ polygon-pattern-file: url("images/orange.jpg");}
[MAP_COLOR = 6 ]{ polygon-pattern-file: url("images/gray.jpg");}
[MAP_COLOR = 7 ]{ polygon-pattern-file: url("images/mix2.jpg");}
[MAP_COLOR = 8 ]{ polygon-pattern-file: url("images/brown.jpg");}
[MAP_COLOR = 9 ]{ polygon-pattern-file: url("images/black.jpg");}
[MAP_COLOR = 10 ]{ polygon-pattern-file: url("images/orange.jpg");}
[MAP_COLOR = 11 ]{ polygon-pattern-file: url("images/gray.jpg");}
[MAP_COLOR = 12 ]{ polygon-pattern-file: url("images/mix2.jpg");}
[MAP_COLOR = 13 ]{ polygon-pattern-file: url("images/brown.jpg");}
[MAP_COLOR = 0 ]{ polygon-pattern-file: url("images/black.jpg");}
}
publish the map with Tilemill to your MapBox account then follow this procedure to make it a basemap in AGOL
Alternatively use the images folder to experiment on your own cats.
Enjoy Your Cats!