Just picking out things I like. Here are some questions I'm asking myself when I look for reference: What parts are interesting to look at? I could just copy a dentist chair form anywhere, but what parts would add to the feel of a horror game, or catch the players attention as an asset? What materials suit the atmosphere better than others and why? Do they fit coherently together, i.e. old rotten wood might look great, but would it be made of this material if the rest of it was shiny white plastic?