This would be a great feature for beginners, though I wouldn’t limit it to Unsplash. Let’s make an easy API for hooking in image services such as this one.
I pondered a bit about this when I wrote the Google Drive FAL integration earlier this year. FAL isn’t designed for these kind of image services, so what’s needed is a search and listing interface that adds images to FAL when you select them for use.
This would also go great with the addition of a thumbnail view in the Filelist module (a suggested feature in Improve Beginner UI Sprints).
Some image banks also have great alternative text, so that should be imported together with the image and photo credits.