So, with my still fresh install of FreeBSD amd64, what was I to do to run the 32-bit only spotify client? Setup a 32-bit environment of course.
I more or less followed what is written up here: http://forums.freebsd.org/showthread.php?p=191438
make distribution, it failed with an error that sendmail's freebsd.cf file didn't exist so couldn't be installed. Looking around the intarwebs, I ran into a number of reports regarding a tinderbox bug that caused exactly this, but I was not using tinderbug. Ultimately, I just ran 'make' by hand in /usr/src/etc/sendmail and "make distribution" worked happily.
Just setting the display in the chroot environment didn't work out for me. Eventually I installed x11-servers/xephyr. Then it was just a matter of running
Xephyr -ac :1in the host, setting the DISPLAY variable to localhost:1 in the chroot environment, and I was able to get Spotify up and running under wine.