Though the vast majority of postcard backgrounds fall into the latter three categories, there are other categories as well.
The Black Backdrop
The use of solid black backdrops was scant, but occurred on occasion:
The Red Background
In this trend, a (presumably) white backdrop was painted a solid, bright red:
This background type appears only to have been used by the publishing house ARS, and not frequently. I have also seen one or two examples of postcards with backgrounds painted blue in the same way, although none are currently represented in this collection.
The Overpainted Background
In this background type, the original backdrop or outdoor setting is painted over in the tinting stage:
The design does not correspond to anything in the photograph itself.
Photomontage–the combination of two or more photographs into one image–was never used as commonly in these postcards as in those of the 1900s and 1920s, but sometimes a bucolic image would be overlaid onto the plain background of the figures:
or the figures themselves would be overlaid onto another photograph: