show everything you have available. that way they can see what al lthey get access to if they convert to full. what we do is give ful users access to ALL of our sites. trials just get access to the site they joined. but it does wonders for converting trials when the customer sees 40 other sites worth of content and can browse through it, but when they try and watch it they have to upgrade.
you could also do it where trials don't get access to the high res versions of clips/pics. or trial members have to wait longer to get the new updates. any number of things you can do. trial and error to figure out what works best with how your members area is setup. i would advise against the "scam route" where a trial has access to like 10 scenes or something and needs to actually upgrade to get access to the bulk of the members area.