Would a 2k11 png work on 2k10?

For example, would I be able to use Dennis Johnsons portrait and Cf in my 2k10 game if I imported it?

the portrait would work if you exported the 2k10 texture and imported it into the 2k11 files

I dont think the CF would work but you can try it and report back if it works or not. (remember to backup your file)