This looks like PVE, not PBS by the way (so wrong forum), but to answer your question, in Content you select what data must be stored on that NFS-share. This data is always put in a sub-folder with a specific name for it and is hard-coded, you can't select a random name or put random data in such a location, only data that "fits" gets put there and is visible.
The only "multimedia" that is probably accepted would be iso's containing said data in an iso-storage, which you can then link to your VM's or Containers, or they need to be a full "Disk Image" or "Container" to have that linked to a device.
If you want to provide "random" data to your VM's or Containers, your best bet is most likely to install NFS or SMB on your VM or Container and link it directly to the storage instead of through Proxmox.
