Looking at a video preview for a spin synth today which begins (as usual http://bit.ly/psfsdvc ) at the center of the arc, I began wondering whether the video preview would be updated to begin at the appropriate place when the author manually chooses a different first photo for the spin (e.g. the far left or right end of the spin's arc).
Joscelin also wonders about the video thumbnail getting updated here: http://bit.ly/psfcbpvt
Yes, all of the various thumbnails, backgrounds and videos are regenerated once a starting image change is requested. Because it is a background process and due to various caching issues, it may take up to 20mins to see the updated content.