It's worth checking this one out as well:
http://videopeek.roundbit.tech/
It's easy to generate thumbnails for single or batch files and also lets you browse the grid "interactively" and jump to certain points. I love it when browsing my collection hahah
It's free for HD videos but you have to pay $5 for 1080p... I couldn't find a crack so I ended up buying and don't regret it
(pic from their site)