Hey there! Did you know you could download your xbox screenshots from xbox.dvr.com or by using the smartglass app? You can also use the Machinima Cam Custom Game option to take screenshots outside of your players POV, just like theater mode.
Yes you may need to add a few more screenshots as if you lack in screenshots it doesn't show much about your map so consider adding a few more. 4-5 on top of the one you already have should work. Also I tried to download it but it takes me to the waypoint home page. Try redoing your download link as well.