There are two applications that play QuickTime movies. One is the QuickTime Player, which is skinnable, and the other is the QuickTime Browser Plugin, which is not.
QuickTime Player gives you all kinds of flexibility because you can opt not to display the player itself, displaying instead another video track with sprite controls (the "skin"). That means the player itself can appear to be any arbitrary shape, although it is worth noting that the movie itself is still going to be rectangular.
You can use this to your advantage on the Web, because while you can't apply a skin to the web plugin directly, you can simulate it by cleverly positioning the movie on the page and blending the movie background with the page background. If you had a movie, for instance, playing in an oval cutout, you could apply a masking track to that movie so that the border of that cutout out to the rectangular extent of the movie was a part of the movie, and then carefully match that track to the graphic on the web page positioned behind the QuickTime plugin. Then for controls you use JavaScript controls on the web page so that you can control the movie with controls other than the usual boring controller (set "CONTROLLER=FALSE" to make the normal controls not appear).
To launch a skinned (or not skinned) movie in QuickTime Player, you have to first get control passed to the browser plugin, since it knows how to start the player. So your image link is a poster movie, as Kirk described, and when clicked its target is the standalone player.
I have an example of this at
http://capital2.capital.edu/admin-staff/dalthoff/patrons.html. The link on the left links to a web page with a movie embedded in it. The link on the right is a QuickTime movie which launches the *same movie* as the one that plays in the left-hand link. The difference is that the movie launches in the standalone player, where it is instructed to open at full screen and to quit the player when it finishes.
You then want to return control to the web page when the movie finishes playing, correct? There are two ways to do that. The simplest is to set your movie to close when it finishes. The other option is to include an HREF track in the movie which can pass certain commands (or URLs at least) back to the browser. Experiment with that one, as Apple has dumbed down the feature a little bit in response to the shoddy programming over at MySpace that allowed QuickTime movies to reprogram peoples' personal pages. I don't know what the limitations are now, but it does still sort-of work.
--Dave Althoff, Jr.