Hey Gamer3000,
A simple way to do if you have a map texture would be to create a UMG widget that displays itself when a certain key is pressed. The widget only needs to display the image so it would be relatively simple.
If you want a “live” view of the area around the player, one of the guys from Epic just created a tutorial on how to make a “mini-map” using UMG. It is not exactly the same, but you could make the UMG widget cover a larger portion of the screen.
Hope that helps! 