I know exactly where this is. There is (or was) a portrait hanging on this black wall. The lighting in this area is actually excellent for the HBG.There's a new Hatbox Ghost rumor. The following was obtained from WDW Radio Disney Forums, posted by member WDW999:
"Obviously this isn't definite as nothing has been released from Disney, but I heard something similar to the hat box ghost could be returning to the haunted mansion in the near future. A friend got this information from a fairly credible source (not a Disney bus driver lol). When the hatbox ghost was first created, effects didn't always work inside the attraction - obviously technology has greatly improved since then. Apparently the new figure will be placed in between the ballroom scene and the attic - there is an empty dark space there now. Actually, if you ride the attraction now and shine a light on that area (while of course being respectful to other riders), there is a hole cut out of the wall and a black drape covering it. Like I said before, this is a rumor as Disney has not released anything, but I hope its right! This would be perfect for the upcoming 40th anniversary of the park and for the attraction! It seems as if the Hatbox ghost has also been showing up in more merchandise, etc. lately - maybe thats a sign as well"
I'm assuming, however, that this member is talking about WDW's Mansion.
With respect to Disneyland, I know more than I'm not telling. (I can't.) Regardless, anything can happen. It has in the past.