I installed Syncthing as per [HowTo] Install and use SyncThing on OSMC
I also installed syncthing on my PC, a Mac Mini in my case. I then created a folder on the PC and a corresponding folder on OSMC. Any photos I want on OSMC I now only have to move to or delete from the PC folder.
This means that I can update the photos on OSMC without logging into SSH or an SFTP client.
I keep updating my photos on OSMC so the screensaver doesn’t get too boring.
Hope this helps.