Marvel Studios President Kevin Feige is a huge Star Wars fan - he's even producing an upcoming movie - and that means he grew up delving into the amazing concept art created by Ralph McQuarrie.
Because of that, concept art is understandably a huge part of the Marvel Cinematic Universe, and since day one, the studio has used artwork to hype up their releases (first looks at the Guardians of the Galaxy and Avengers: Age of Ultron were revealed that way). When movies come out, so do books packed full of art, while the artists who work for Marvel frequently share their designs on social media.
Not everything ends up influencing what winds up on screen, of course, and there are some incredible, unused ideas which never make it beyond that pre-production stage. Sometimes, it's easy to see why they were overlooked, but there are a lot of ideas which definitely shouldn't have been ignored.
While it may seem like it's too late for those incredible pieces of concept art, there's no reason to suspect that they couldn't be used in any of the upcoming Phase 4 movies and TV shows...