Custom thumbnail in embedded player

[inwardmovement]

Provide a way to set the thumbnail from the embed code like the poster attribute of the native HTML player.
Use case: display the same video with the right thumbnail according to the context, for example a thumbnail with brand logo when the page includes only the player, but a thumbnail without the brand logo when the player is in a list of videos with brand navigation.
For now we have to upload the same video twice and set a different thumbnail for each.