Here is a choice of outline blank world map images, which have transparent areas. There are three possible cases with transparent areas in this group: land areas are transparent and water areas are white, or water areas are transparent and land areas are white, or both areas are transparent at the same time.
Code of the map: b2b
Land color: white
Water color: transparent
Outline thickness: medium
Code of the map: b2a
Land color: white
Water color: transparent
Outline thickness: thin
Code of the map: b1a
Land color: transparent
Water color: transparent
Outline thickness: thin
Code of the map: b1c
Land color: transparent
Water color: transparent
Outline thickness: thick
Code of the map: b1b
Land color: transparent
Water color: transparent
Outline thickness: medium
Code of the map: b7a
Land color: transparent
Water color: white
Outline thickness: thin
Code of the map: b7b
Land color: transparent
Water color: white
Outline thickness: medium