It will depend on the situation if it is just a view from one or two windows or the entire structure and terrain.  You can use an actual image the way chief does 2D plants and rotates them so they look 3D. Or you can make a giant or maybe not quite so big polyline solid as Larry did and apply your background image as a material.  I have done a complete cylinder around my entire project but the issue with that is that it blocks the sun so that you have issues with shadows but maybe if you did one