Need help finding an image viewing app for BoX map images

[TG-55Panthercules]

In trying to figure out how to use the new overlay capabilities in the recent Oculus Home beta update, I've encountered a problem I could use some help with.

 

Every image viewing program I've located so far always displays the map image with a typical Windows border around it (such as the one below):

 

 

I need to find an image viewing program that allows you to get rid of the borders and displays the map image edge-to-edge in a resizable window (so it would look like the one below):

 

 

Anybody know where I might find such an image app?

Edited December 9, 2017 by TG-55Panthercules