If you need multiple files, you need an archive first, such as "tar", which would then become ".tar.bz2" after being further compressed. The download system does not understand that files, and expects that individual files are being bzipped.
You cannot combine files into one with sv_downloadurl, however, if you're creating a map, you can include the relevant files for that map within the map file instead.
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Mostly known as "DarkDeviL".
Dropbox FastDL: Public folder will no longer work after March 15, 2017!
For more info, see the [SRCDS Thread], or the [HLDS Thread].