Detz, we also have Videos of our apps on our site and even say so in the iTunes-Description...so...all I can say: don't think people will a) read the description for more than one sentence and b) come to your website and watch the movie!

)
Ok, that's a bit unfair...some people came over to see the movies and some even read the manual of TouchScan!!! But all in all I'd estimate there were only about 10% reading and coming over to the website.
Anyway, it won't hurt to release some screenshots and videos! But you should definetly rethink your strategy with the free version...you will release about 17% of your game for free...almost 1/5th...pretty much for a teaser!
Think about a start-promotion with "Free for the first 1000 downloads" or something...I'd say that's a better way to go.