The smaller the better. It's almost impossible to tell what the video is from the thumbnail unless there's a big fat screencap of the main character in the thumbnail, so I need to read the title of the video 99% of the time anyways. Make the thumbnails as small as possible, I say. I think the sizing before Sea Serpent went live was just fine, as they were about as small as you could get, given that some video titles are like 12-15 words long. The new size of video thumbnails in Sea Serpent seems unnecessarily large.