Yes you can on business accounts! Our system supports audio files (.wav, .mp3) for your own music on hold or advertising on hold. We can do it company wide, per queue (such as sales or support), and even down to per user. Make sure you have rights to the content. This change must be done by our friendly VOIP admins so please contact support to get this done.
We have no affiliation with these, but here are some links to some sources of royalty-free hold music:
easyonHold – All types of music to fit your business type
Pleasehold – Advertising or commercials on hold