Pixave is one of the best image organizer apps available for macOS. What Apple’s Photos.app does for your photos and iTunes does for your music, Pixave does for your images. No matter what you throw at it, it neatly organizes them for your in its library. You can create multiple collections in the app, and tag your images the way you want.
I have been using it for several months now, and it’s a great way to deal with the mess created when you work on multiple websites at the same time. Look forward to the feature on Beautiful Pixels very soon.