If you're doing environment concepts for a room that will actually have gameplay, paint over a grayboxed room and/or after having talked to design to see how the room needs to work. Otherwise, we all ooh and ah over a beautiful environment concept, and then immediately trash everything except a handful of elements that we…
General rule of thumb: 1/ Don't make impossible shapes. Things don't have to line up perfectly in an ortho, but as long as they roughly work, then it's fine. Leave the non-euclidean stuff to the designers. Generally if you can sketch out a few views of different components or sub-sections it'll weed out the impossible…