A character that I want Lucasfilm to expand upon is Darth Bane. Darth Bane is known by fans as the creator of the Rule of Two. The character was created by George Lucas in the 1990s as part of his backstory for the STAR WARS PREQUEL TRILOGY.
Darth Bane's first mention in Star Wars is in the novelization of THE PHANTOM MENACE, which is written by Terry Brooks and published in 1999. In Terry Brooks' memoir "Sometimes the Magic Works: Lessons from a Writing Life," he claims George Lucas spent an hour on the phone with him discussing the history of the Jedi and Sith for the Episode I novelization. Information on Darth Bane is brief in the novel for Episode I, but it is worth noting that they refer to Bane's Sith apprentice as "him." This is obviously different than the Expanded Universe/Legends brand, which had Bane's apprentice as a female (Darth Zannah).
The Expanded Universe/Legends brand expanded upon Darth Bane's history. First with the Dark Horse Comics mini-series STAR WARS: JEDI VS. SITH, which was released in 2001. Second with the Darth Bane novel trilogy published by Del Rey. This trilogy was written by Drew Karpyshyn and the books released in 2006, 2007, and 2009. It's important to note that the Legends brand stories of Darth Bane are not connected to George's version for his backstory to the Prequel Trilogy and THE PHANTOM MENACE novelization.
George's version of Darth Bane finally made its on screen appearance in season 6 of the television series STAR WARS: THE CLONE WARS. His official look being very different from his Legends brand counterpart. Concept art for the official canon version of Darth Bane was created by Darren Marshall. Darth Bane was voiced by Mark Hamill in THE CLONE WARS series.
It will be interesting to see how close Lucasfilm will stick to George's version of Darth Bane. Do you want to see Lucasfilm explore Darth Bane's history?