Basically, 3D Lighting and Particles, in a 2D game. Is that possible?
Hi NorseHorse1492 -
The short answer is yes, though the tools that were used in Rayman Legends are not in the engine. You could develop a series of flat planes creating an illusion of 3D depth. You would have to do some work on either hand painting your lighting or really controlling the location of lights and how they are used and what they are influencing.
Thank You
Eric Ketchum
(converting old answer to a comment since it was a reply to an answer)
And spline components are going in to the engine very soon. That means you should be fairly easily be able to extend editor functionality and make your own spline based level creation tools 
This is something I have though about a lot both because I LOVE rayman (just beat Origins, best end of game credits of any game ever) and because I have worked on background art elements for Fortnite. The rayman stuff definitely inspires a lot of creativity!