The Mercury Messenger rev 12 data will be made public by PDS in September, 2014. I hope it has elevations for the Southern Hemisphere!
Mercury 10x Globe:
The North half of the planet Mercury is detailed with an exaggeration factor of 10 for the elevations.
PDS info (Planetary Data System)
INSTRUMENT_HOST_NAME = "MESSENGER"
INSTRUMENT_NAME = "MERCURY LASER ALTIMETER"
INSTRUMENT_ID = "MLA"
MISSION_PHASE_NAME = {"MERCURY 1 FLYBY","MERCURY 2 FLYBY",
"MERCURY ORBIT","MERCURY ORBIT YEAR 2"}
TARGET_NAME = MERCURY
START_TIME = 2008-01-14
STOP_TIME = 2012-09-17
PRODUCT_CREATION_TIME = 2012-10-31
PRODUCT_RELEASE_DATE = 2013-03-08
PRODUCER_ID = MESSENGER_MLA_TEAM
PRODUCER_FULL_NAME = "DAVID E. SMITH"
PRODUCER_INSTITUTION_NAME = "NASA/GODDARD SPACE FLIGHT CENTER"
DESCRIPTION = "This data product is a shape map (radius)
of Mercury at a resolution of 21.293 km/pix by 21.293 km/pix,