‘Starborn Wanderers’ is a free-to-play sci-fi RPG. Their colorful One Pager is absolutely packed with incredible old-school illustrations and a great reference of parallax scrolling done right! Make sure you use the right nav to scroll as the parallax is smoother.
This website has unfortunately been redesigned or gone offline, so I have removed the direct link to it. The screenshot below hopefully preserved enough of the design but if you are really keen to inspect further, try this Archive.org link. FYI: the site was first featured on 04 July 2013.