Maps are actually images, so just download the image upload it and run the game!
I have already made a couple just for fun!

Templates/Empty

Earth

Islands

Japan

Islands 2

Logo

 Large World (Edit cell size, and change ship range to 15!)

Custom Nations

Large WW2 (Edit cell size, and change ship range to 15!)

WW2

 Sengoku Japan

Not a map, but it is a rule Set:

{"#b6b6b6":[35,125,["Japan","Germany"],"Italy"],"#5b0000":[100,200,["Japan","Italy"],"Germany"],"#fe3636":[100,175,["Germany","Italy"],"Japan"],"#c03939":[250,200,["UK","France","USSR","Austrailia","French Africa","India","China","Poland","Canada"],"USA"],"#800000":[70,100,["France","USSR","Austrailia","French Africa","India","China","Poland","Canada","USA"],"UK"],"#ff5c5c":[10,210,["UK","France","Austrailia","Poland","French Africa","India","China","Canada","USA"],"USSR"],"#1c0ea6":[150,10,["UK","USSR","Austrailia","French Africa","India","China","Poland","Canada","USA"],"France"],"#f65cff":[10,150,["USSR","UK","France","Austrailia","French Africa","Poland","India","Canada","USA"],"China"],"#73a1ff":[50,90,["UK","USSR","Austrailia","French Africa","France","India","China","Poland","USA"],"Canada"],"#1dbbb2":[35,25,["UK","France","USSR","Austrailia","French Africa","India","China","USA","Canada"],"Poland"],"#3aff51":[15,14,["UK","France","USSR","Austrailia","India","China","Poland","USA","Canada"],"French Africa"],"b16333":[35,60,["UK","France","USSR","French Africa","India","China","USA","Poland","Canada"],"Austrailia"],"#72594b":[35,80,["UK","France","USSR","French Africa","Austrailia","China","USA","Poland","Canada"],"India"]}

the website I used was http://jsoneditoronline.org/