On headless machines, start the container server with
%%CONTAINERFLAGS%%="-Djava.awt.headless=true"
to prevent problems showing album art thumbnails.

You can increase the container server's memory allocation if needed like
%%CONTAINERFLAGS%%="-Xms96m -Xmx512m"

Use a UTF-8 locale to enable support for all possible tags. Otherwise,
files with Unicode tags will not scan properly and will be unplayable.
Chapter 23 of the FreeBSD Handbook has information on using locales.
https://www.freebsd.org/doc/handbook/l10n.html

For example, US English:
%%CONTAINERFLAGS%%="-Dfile.encoding=UTF-8 -Duser.language=en -Duser.region=US"

Combine multiple flags into a single %%CONTAINERFLAGS%%="[...]" line.