Instead of putting bitmap image in BG Vray options,you can draw arc "wall" behind your windows(i prefer it better instead of putting image in BG slot,because i used for Sun)
you can draw closed arc plan,push it above,make group,delete all the faces except your arc vertical surface,import your landscape image on the arc surface,right click - texture - projected- go to paint bucket,chose sample paint,click on your image,pick paint bucket again,and color your whole arc surface
model_1.jpg