if the things you're collaging can't be copyrighted because they lack human authorship, you can only copyright the arrangement, not the things you're arranging.
If they have human authorship, its the original human artist's work you're collaging and now you're creating an unauthorized derivative work violating many copyrights.
If they have human authorship, its the original human artist's work you're collaging and now you're creating an unauthorized derivative work violating many copyrights.