Gallery mode for project panel
There should be a button on the bottom of the project panel to toggle "Gallery mode" which would show thumbnails for all of the assets in your project. Or perhaps there is a new "Assets" panel instead of replacing the project panel, which might be more useful.
This would operate somewhat like Adobe Bridge, allowing you to quickly and easily view images in high resolution. It should also be able to scrub/play videos similar to the Premier Pro project panel.
This would be a very useful feature that I am sure many, many After Effects users would enjoy! It would be relatively easy to code and I know plenty of people would use every single day.