One thing I always did when selling was take pictures outside instead of in the garage, running or not. I polished it, cleaned it up really good. Again, that was just my preference and to many it might not make a difference. Plus it depends if you are selling it as a project or fix to drive.
It is definetly a psycological thing because a dirty car might be in perfect condition, but it just does something to your brain when you see a shiny car vs. a dirty one. I always felt my car ran better after I waxed it? Sounds crazy?
When a stranger comes, and even if it has some rust, mechanical issues, that car out in the sun all polished, clean windows, shiny tires and rims, it just sets off something in the brain that gives the car a positive vibe.
Again this is just my 2 cents for what it is worth. I really like your car and hopefully you will get what you want when you try to sell it.