My sources of inspiration are varied but one technique I like is that of posterisation in pictures (not photographs) for the 1930s and 40s. To produce what I want needs a lot more effort than just using the simple posterisation effect in Photoshop. Here I show a sequence of images that build up to get (almost) the effect I am after. Note that the selection of different parts of the image is rough and ready – this is because I am exploring the technique, not making a finished product!
The enhanced detail may not show well, so below I show a magnified slider comparison of the posterised version both with and without the detail: