Step 1: Select a prototype (if you're going to base it on one) and find photos. Ideally, you're going to want shots from a number of different angles, highlighting detail elements, the cab roof, both ends of the tender (if it has one), the front of the boiler, the interior of the cab, etc. A great resource for this is traditional model trains - especially brass locomotives, which are often resold on the internet with accompanying photos. Remember: if you cannot directly right click to save a...