Video Gallery Index

I am loading a large format preview image in to promote video (350 x 800) like a billboard in a large slider preview panel. the video plays in that same sort of panel if selected. my issue is how to get a good looking small thumb for the video index page. right now these small preview images look like random cuts of the larger image. is there a tool that could help manage this or do i need to load up a small version of the image as well? any help would be greatly appreciated.