Add ability to have more frames in the video thumbnail

[grimatoma]

Currently the thumbnails for a video is only 4 frames but in most cases this is not enough details to know what video it is. I often use very large thumbnails and it would be really great if I had the option to do a 3x3 grid.
Alternatively have the ability to customize it.
Either way having 9 frames would greatly help and I hope the level of effort is pretty low for this.