the easiest way would be to do it in the player not the video ( i.e. a playlist ) , then you can change the image dynamically
windows media player and flash both offer the use of playlists.
Heres an example of how to do it with window media player.
open any text editor copy and save the following as example.wvx
Code:
<ASX version = "3.0">
<ABSTRACT>www.abstract.com</ABSTRACT>
<TITLE>a title</TITLE>
<AUTHOR>Smokey</AUTHOR>
<COPYRIGHT>www.yoursite.com</COPYRIGHT>
<Entry>
<Banner href="http://banner.com/image.jpg">
<MoreInfo href = "http://bannerurl.com" />
<Abstract>click me</Abstract>
</Banner>
<Ref href = "http://www.avideo.com/avideo.wmv" />
</Entry>
<Entry>
<Ref href = "http://www.avideo.com/apicture.jpg" />
</Entry>
</asx>
you can play the file in widdows media player or vlc or pretty much any video player, embed it pretty much the same as a wmv