From TEPCO's Photos for Press page, 4/16/2012:
Two videos showing the fuel rack:
One of the two videos showing the fuel handling machine:
Unlike the Spent Fuel Pool of Reactor 4 which was nearly full with fuel assemblies, the SFP of Reactor 3 was only about 46% of the capacity (514 spent fuel assemblies, 52 new fuel assemblies in the pool that can hold 1220 fuel assemblies, according to the Ministry of Economy, Trade and Industry document from March 2011).
Concerning the MOX fuel in the spent fuel pools at Fukushima I Nuclear Power Plant, the November 2011 report by the Institute of Nuclear Power Operations (INPO) says (page 35):
"There are no mixed-oxide fuel assemblies in any of the spent fuel pools or in the dry cask storage facility."
You can download the report here.