Unity Asset Store - $10 Corral images where you want them with this Image Viewer plugin. Select a bunch of images in the Project window and this viewer will allow you to pin them inside the Image Viewer so you can keep them in view at all times. Image Viewer 1.0 Video Image Viewer 1.1 Video Features: - Pan/Zoom or Fit the image to the window - Multi-image pinning - Multiple Image Viewers that can be docked together (native function of Unity) - More features coming soon in version 1.1 Image Viewer Lite *free* Features:- Fit to window - Multi-image pinning - Multiple Image Viewers that can be docked together (native function of Unity)
For the convenience of having your images shown inside the editor at all times. The paid version has a few extra features for the ones that want it.