How to change video picture

I'd like to recommend AVS Video Editor to you, I always use it to edit video and make funny video for uploading to Youtube, it's easy to use and the quality is awesome, you can crop, cut, join, edit video with it easily.

You can only choose one the 3 thumbnails i think. Or you have a premium affiliate account with them.

Hmm, Still got the option over here, I still can upload pictures from my hd as thumbnail for my yt video's.. And as far as i know, I'm a yt partner and nothing more or less.
It could be a "country" thing, Lot of people over here have an new yt layout (Netherlands) with these options (thumbnail upload, Invideo programming, Dashboard etc).

I also think that a video editor will not pleasure you on this problem, yt will still give you three thumbnails to choose from... Try too determinate at what moment these thumbnails are taken in your video... Probably Begin - Middle - End, Try to at some "extra" at the end of the video and look what happens... Not working? Try an other timing... Try, try, try that's what i did...