If there is a nice (wide/panoramic) view around the plan (as in one of my projects) it is also possible to use a 360° panorama picture as sky texture, as the first example image below illustrates. Some photo experience makes it easier. But it is also possible to cut and paste a panorama from a street-view service. These two links give advice on aligning sky/horizon textures: 5976 Add horizon, and 5533 Floor Texture - Adjusting Problem
Or, as discussed here, just objects with texture images (could be semi transparent) flat, concave or convex is one way of doing it. The second example below uses a slightly curved object with a picture of a treeline. The sky is made transparent (removed) from the image on the object), so the SH3D sky will be visible in the background. The nice thing about the curved treeline, is that SH3D sun will render nicely along the treeline depending on time of day (very nice for sun simulation movies).
Both these methods have the advantage of not filling the plan with lots of trees and other outdoor objects that bloats the file, yet they will give fairly realistic renderings. And for me, it is quite important to be able to test what the view out the window will look like. For instance, will I see sun setting on a mountain from my favourite chair...
Or, the two can be combined. Horizon in the background - treeline (or whatever) in the front. Failing all that, some creative photo-editing of the rendered photos can also create cool pictures.
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Panoramic image as sky texture:
Curved object with image of trees, transparent at top (sky texture is just a gradient image seamless, 360°):
