With 2D, perspective difficulties sometimes develop in the foreground of the scene, portrayals of the far distance and skyline are really similar to 3D, so it’s best not to be too ambitious, mainly because you can’t introduce a believable perspective convincingly or gradually enough, and some of the generic ready made ones have this trouble.
As long as there is a certain freedom with the design, the best features to represent on absolutely flat rear panels are layout scale ones like parallel lineside buildings or retaining walls.
A small part of a painted 2D scene, without any difficult perspective or a visible skyline. Scenes like this suit narrow baseboards in areas like the approaches to branch line stations and are easily blended into countryside/village layouts. By introducing some colour matched late summer foliage done in low relief, it could be arranged into a gap, possibly breaking up thicker wooded areas.
2D Acrylic painted panoramas like this one can be produced to order, with horizon heights to match other existing backscenes.
2D rear backscene panel detail below the skyline.
2D scenes like this example can be brought to life in very low relief. Windows, sills and other details can be added, and with a few shadows, and some weathering and blending in, a scene like this could come together as a charming small collage.