"Doctor Strange" director Scott Derrickson tweeted an image which may give a hint in regard to the film's plot. Thanks to Cinema Blend for the tip.
The image above is taken from "Doctor Strange: Into Shamballa," a graphic novel by J.M. DeMatteis and Dan Green from 1986. The story starts with Strange visiting the home of the Ancient One in the Himalayas. Once there, he discovers his former master has left one last gift for his erstwhile pupil...but it is a rather perplexing one.
Before we go any further, if the image is a hint that the film follows the plot of "Into Shamballa," here's your SPOILER WARNING for Doctor Strange and "Captain America: Winter Soldier."
Back in August, IGN reported that the "Doctor Strange" film would not be the story of the Master of the Mystic Arts origin. However, during "The Winter Soldier" Jasper Sitwell drops the names of both Bruce Banner and Stephen Strange as enemies of Hydra who need to be eliminated. Therefore, it is possible that "Into Shamballa" could tell the story of Doctor Strange becoming Sorcerer Supreme.
During "Into Shamballa," Strange interacts with the Lords of Shamballa, which has the potential to fold into the story of Strange gaining power without it being a full-blown origin tale.
Not long after tweeting that picture, Derrickson sent out another tweet, which you can read below (NSFW), so all of this speculation may be for naught.