A couple of nice engine turning images I located:
Turntables at Frostburg, MD
Image by jimforsberg
took the Maryland Scenic RR from Cumberland to Frostburg, MD where they turned the engine about and we returned to Comberland
A Run Up The Yard – 46521
Image by Sir Hectimere
Severn Valley Railway mogul No. 46521 on test after a quick running repair, takes a turn up and down the shed yard at Bridgenorth.
Camera: Olympus OM1 35mm SLR.
Vulcan steam train
Image by stratman² (2 many pix and busy)
Old train engines have been designed to pull forwards rather than push backwards. Due to the fact of this the only way for the engine to be in front of the carriages and pulling them is to physically rotate the direction of the train engine on a huge turn table like in this image.