MM is based on an OLD version of YM, so maybe the support forum for YM could be useful. It's possible MM will do it but it's all about the right strategy. Are you using the gallery shortcode (built-in gallery)?
Try something like this:
Code:
[no_access]img thumbnail + teaser text[/no_access]
[private]img/video[/private]
http://www.yourmembers.co.uk/forum/v...allery#p320 4