They include images that show parts of the surface missed by the Mariner 10 spacecraft when it flew by the planet in the 1970s.
Like the previously mapped portions of Mercury, the new sections appear heavily cratered.
Messenger needs to perform another two fly-bys and a number of engine firings to get itself into orbit in 2011.
Monday's manoeuvre took the probe to within just 200km (125 miles) of the planet at closest approach.
Messenger was programmed to collect more than 1,300 images and make other observations during the encounter.
The 700GB of data began transmission to Earth on Tuesday.