There's around a dozen unpublished pieces that were discovered after Chopin's death. Some of them have only come to light comparatively recently and are available inexpensively in published collections. A few seem rather sketchy and probably would have been more fleshed out and refined if they ever got to be published. One of my favourites is the Nocturne in C# m 'Lento con gran expressione', Br.49 .
There are reports though that some works were refined to become more genteel for publication.
The Waltz in Amin (as noted in the
http://www.classicalmidiconnection.com/cmc/chopin.html link sent before) is numbered as Br.150 in the M.J.E. Brown index of Chopin's works.