The art of a Pass: Polish
So, a this point you've built your level: it feels the way it should with encounters and puzzles feeling well rounded and interesting. The design at this point should invoke every aspect you were designing for, all without the artistic flourish of lighting, clutter, and maybe a little tweak here and there. This is where you make things pretty and effectively communicate player path for those unused to your level. This also is going to take several attempts, this isn't like the other passes where you do one, test it, and usually it all checks out. You'll see a little thing out every now and then, you're going to find ways to better optimize that particle effect, or use that rubble in a much better spot. Polish passes likely would never end if you let it, so at some point you will have to declare it "done" at some point or another.