Interesting approach to a a very interesting challenge, given how close the images supposedly are.

With the limited training data they have I'm surprised they don't mention any attempts at synthetic training data. Make (or buy) a couple museum scenes in blender, hang one of the images there, take images from a lot of angles, repeat for more scenes, lighting conditions and all 350 images. Should be easy to script. Then train YOLO on those images, or if that still fails use their embedding approach with those training images.