Hi,
Yes, you can use the remaining 10Gig interfaces for whatever you like. They are just like any other 10Gig interfaces.
Breakout command config guide:
http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus6000/sw/interfaces/6x/b_6k_Interfaces_Config_Guide_Release_6x/b_6k_Interfaces_Config_Guide_Release_602N12_chapter_0101.html
HTH