Things that enhance a layout usually are details that are subtle, different, and sometime small. It is surprising what visitors to your layout will remember, so not always is it the "Big Boy" or the 3 tandem diesels but could just be a creek drainage pipe. Found this picture, would make a wonderful addition to any train yard and so easy to do. They are literally 100s of G scale toy engines to be found in thrift shops across the US, check them out. Box cars on small platforms also make interesting themes, and once saw 4 or 5 cabooses set up like cabins in a scene.
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