Youtube announced some new features that will allow viewers to see an image preview or a series of thumbnails.
Sneak Peek: Hover your mouse over the seek bar and a thumbnail of that moment will appear, and you can click to start watching from that moment.
Scanning Through Thumbnails: Drag the handle along the seek bar to show a filmstrip of thumbnails of previous and upcoming scenes.
Zooming in on Long Videos: Zoom in on the seek bar, one and a half minutes at a time. This second bar that appears gives you more granularity for finding that exact moment you want on a long video.
I wonder if this means that non-partners will have more than 3 thumbnail options since Youtube will essentially be pulling multiple stills anyway. This is my number one desired feature. Kudos to Vimeo for being a little more flexible.