Last week the new Star Wars book Jedi vs. Sith: The Essential Guide to the Force came out. I haven't bought it yet but might later this afternoon (and I found these images on Wookieepedia). Within it, hauntingly painted by Chris Trevas, there is the first-ever "canon" image (meaning it's fully approved by Lucasfilm) of Darth Plagueis. If you saw Star Wars Episode III: Revenge of the Sith then you already know that Darth Plagueis was the Sith Master who trained Darth Sidious. He was also obsessed with stopping death.
So here it is: Chris Trevas' portrait of Darth Plagueis (watching a young Sidious spar with a lightsaber):
And here's a close-up of the face of Plagueis:
Even though that's just one picture, that's still an awful lot more about Plagueis than has been released since Episode III. There was going to be a novel about Darth Plagueis that James Luceno was working on, but it was cancelled mid-stream 'cuz Lucasfilm announced that George Lucas wanted to keep a tighter grip on the Plagueis/Sidious part of the Star Wars backstory. Might this mean then that we might start seeing more about Darth Plagueis? Let's hope so! :-)