I have assembled six (small) sets of maps – take a look at each and see if you can categorize them
Set 1
http://www.mapsofworld.com/images/world-political-map.jpg
http://www.mapsopensource.com/images/usa-political-map.gif
And a note on these:Â http://mark-twain.classic-literature.co.uk/tom-sawyer-abroad/ebook-page-08.asp
Set 2
https://mapswire.com/maps/world/world-physical-map-mercator-large.jpg
https://mapswire.com/maps/world/world-equirectangular-blank-physical-map-large.jpg
Set 3
Set 5
http://www.sourcewatch.org/images/thumb/1/16/PA_Marcellus_Shale_Formation.jpg/680px-PA_Marcellus_Shale_Formation.jpg
Set 6
https://en.wikipedia.org/wiki/File:Snow-cholera-map-1.jpg