Reposting question from https://www.reddit.com/r/askscience/comments/5e1zhy/what_does_mercurys_orbit_really_look_like/ which reads:
First the full question: What does the orbit of Mercury really look like visually, without artistic liberties taken to amplify the eccentricity of the orbit, or simplifying it to appear as a perfect circle? What eccentricities are needed for orbits that readily appear elliptical?
I originally did this as a self-answer, but my answer was of such poor quality I've now deleted it. I hope to do a better answer backed by some calculations, but, as always, anyone else is free to answer.