Jennifer Lang says this exhibition has lots of old photos and maps of Central, and is well worth a visit. It's on at the Rotunda in Exchange Square.
More information: http://www.hkland.com/data/media_releases/2015/hll_20151005.pdf
And the accompanying e-book (408 pages long!) about HK Land's history: http://www.hkland.com/125_anniversary/index.html