I attended a technical presentation by Fregonese Associates at Envision Utah on doing photomorphs--aka changing streetscapes over time.
Photomorphing--it doesn't have to be that good--just good enough to fill the eye, and let the brain fill in the rest. Start with a good image--maintain consistent lighting--minimal shadows. Picture big enough to convey changes in roadway right of way and streetscape. Enough 'blighted' or underused private property that can reward changes over time. Can shoot down centerline of street, or from one of the sidewalk corner, at edge of property lane. A 30-60 angle, to see down one street, to explore nature of pedestrian environment.
Add buildings--take a picture of a building you like, or cut it from your library--get perspective right, to get vanishing points right, take picture from the same angle. Use the transform features in photoshop to distort the building so it matches the picture.
Same for people and cars--rough cut out, including shadow, scale them basically right, pop them in. To scale people, use the height of the building. Follow vanishing lines. Taller buildings a little more complicated, because of lens distortion, but not much.
Spend the time to get shadows in, even if poorly done. To make a shadow--take a copy of the image, adjust brightness to zero to make them gray, then reduce transparency, then use the transform tool to distort it and squish it down so it sits and the feet.
Frego has entire LIBRARY of people and buildings and objects. Frego uses their pictures and cutting out the people. .png format. Frego has a library of about 30 people that they just use and re-use. Commercial Version is ArcVision.com--a photoshop plugin that provides a library of trees and people and images, including rotating people to many angles.
Cars can be tricky--may need to remove some cars. Use clone tool to clone nearby area, and paint out the other area. Follow the same vanishing plane. Aligned--pull from same distance from the point. Aligned--duplicate from original alt-selected point. Try to keep color profile identical to surrounding area.
Clean up the base image of temporary or obstructing items (cars, cones, power lines, streetlights). Use shadows/highlights to brighten things up--balances highs and lows of over and underexposure. Can automate a batch function in photoshop to do a series of tasks.--like records a macro in excel.
Corner bump-outs a big deal--reducing walk-out distances to cross the street. Wider streets actually SLOW traffic, because the width of rode requires longer pedestrian signals, due to ADA accessibility. 30 seconds on Seventh East.