I believe you are talking about a posterframe. Depending on how you’ve built your website and how you’ve added the QT component, you may have the option of setting a thumbnail (a jpeg screenshot) or to select the posterframe (a dynamically selected frame from within the video itself.)
I use flash for web video content and most flv video components give you the option of setting a thumbnail image that works as a placeholder until the play button is pressed. (like YouTube) You should find the same kind of options within your QT component.
All the best,
Simon
“Is it me or do I spend half my life watching little grey bars turn into little blue bars??”