With only one channel you could substistute the Video overview block with a Newest video block on the front page. Set it up to show something like 18 thumbnails and show thumbs using the default thumbnail settings for the site.
Now, you've got yourself some content... The standard, small square thumbs are usually not you best option -- so try setting it to use a larger thumb (200px or even larger). You'll need to tweak the number of columns in your Page content configuration after you do this to make the content stay within the lines.
Another good option is to have some explanation on the front page. You've already got some text in the right sidebar, but that can be featured more heavily on the front page on top of the videos.
Then there's the great un-design of demodag.org, which could be reused. Obvious additions would be using full width (#frame {width:98%;} etc) and even dropping the sidebar all-together and having sharing/subscribing/donwloading options below the video player and the content.
Just a few suggestions...