During the early phases of X-Men Apocalypse's production, Elle Fanning was in the running for the role of the 1980's incarnation of Jean Grey. While she lost out on the role to Game of Thrones' Sophie Turner, there was concept art drawn up to showcase the Neon Demon actress embodying the role. Whether it was because the artist really liked Fanning in the role, or if negotiations were further along than the public ever knew, this art has recently been released to the internet, and you can see it below for your own curiosity.
Gregory Hopwood, a costume assistant on X-Men: Apocalypse, shared this photo from Alan Villanueva's early concept art from the film's design phases, and it's rather interesting as it's closer to one of Jean Grey's actual comic outfits. As you can see the image below, the actual costume that Sophie Turner wore in the final film maintains the color scheme that Villanueva's original design shows off. However, the Fanning variant has two big differences.
The first big difference between the final X-Men: Apocalypse costume and the concept presented above is the lack of a facial component. With Elle Fanning's Jean Grey, the costume extends upward with chin and cheek guards, and a headband component to cap it all off. Sophie Turner's version of the costume did not have any facial or cranial features to speak of.
Second, and more importantly, the final design of Jean Grey's costume, much like the rest of the uniforms for the X-Men in X-Men: Apocalypse, look more like like standard big budget jumpsuits for superheroes. Meanwhile, Fanning's potential costume looks more like a comic ready costume that foregoes realism for more of a fantastic look. Take a look at the final Turner variation from X-Men: Apocalypse in the photo below, for comparison.
If only X-Men: Apocalypse had embraced the more comic book elements of its source material, it might have seemed more excited to tell the story it settled on. But then again, Bryan Singer's approach to the X-Men series has always been more anchored in a sense of realism, so to have embraced such an approach would have required a wild deviation from the current formula and/or a director different than Singer at the helm. At the very least, Singer can be considered consistent, above any other problems folks had with X-Men: Apocalypse.
X-Men: Apocalypse will be available on Digital HD on September 9th, with the Blu-ray / DVD release set for October 4th.