Can I use stock or “royalty free” music or art?

It depends. Stock or “royalty free” music or art is accompanied by very specific conditions in the license as to what uses you can and cannot make, and is limited by what rights the seller has to give you in the first place and what protections the seller offers. While you may be able to use certain stock or royalty free music or art in creating portions of your work, you must be the copyright owner of an original work to distribute it through UnitedMasters.