Bigger thumbnail images?
Screen resolutions seem to be getting bigger every year. A few years ago, 800 x 600 px was the most common resolution. Now, it's pretty usual for people to be viewing your carefully crafted website with resolutions of at least 1024 x 768 and, in a lot of cases, 1280 px or bigger.
With the advent of larger screensizes, the old 'default' thumbnail image size of 100 x 67 px starts to look quite small. Does this mean that thumbnails should be bigger as well? The counter argument is that with websites appearing on a mobile phone on a more regular basis, there is still a place for the 100 x 67 px thumbnail.
I guess the answer is that the thumbnail size should be appropriate to the website design and the target market rather than being some 'generic' size.