Though the Korg Kronos comes with some excellent acoustic pianos, you can never have too many acoustic piano options, am I right? Below find a variety of free/public domain piano sample libraries that I've brought over into Kronos format. Some of these are excellent. Several are fairly ambient and might work best for recording vs. live performance.
I would like to thank Bigcat Instruments for providing the Iowa and London pianos in Kontakt format which allowed for easier conversion into the Kronos. Please support Bigcat Instrument