I use a Mac Pro as my favored control for edits and such. Most of the time, the drag n drop feature for new artist pics does not function reliably. I vaguely recall a time when I could drag n drop pics, and there is every indication it should work, but it hasn’t worked for me in quite a while.
If this feature won’t always work, I’d recommend removing it. But I’d rather you fixed it.
PS: if your code is some well-meaning copyright protection effort, that’s okay, but tell the user that’s why it isn’t working. Also, know that such code is easily defeated.