Pause Menu Map



Hi, I have an image for a map that I would like for the pause menu in-game and would like to know the best method of getting it to the YTD files that the game uses.
The size of the image is 4144x5624.
I have the map files for the game and I have made it into 6 sections but not sure if there was a better way/correct way to get the sections then just to get the half and third of the dimensions.
Would also like to know if there are requirements for the map.