Excellent tips.
I might also add that while you're selecting which sample thumbs to put on the preview page, give thought to the order in which you're placing them. I'd have a tendency to put the very best of the selections in the upper rows in case the surfer is too lazy to either scroll or scan down the page, or just in an extreme hurry. Have the best images hit the surfer at the optimum eye level on the screen.
If you're surfing other sites yourself, keep notes on what kind of visuals in the thumbs catch your own eye the most. Its subjective, of course...but if you consider yourself to be somewhat average in taste - possibly what catches your attention also catches the attention of the average surfer. So keep those notes in mind when selecting the order of the thumbs on the page.
Just my
