I'm pretty sure the images of Cookie are from the original into from the sketch. I could be wrong, but that's what I recognized.
If you can identify a speciffic Monsterpiece Theater sketch just by looking at an ordinary still of Alistair Cookie in the usual set, with nothing speciffic happening (i.e., he doesn't hold a shoe or a doll, characters from the featured story aren't in the living room with him, etc), then you must have an amazing talent!
I watched the original introduction for Gone with the Wind a few times, and can't quite tell if that's it. I also watched the intro for The King and I and can't tell. And I watched a few other introductions, couldn't determine if it was any of those. Maybe it'd be easier if I printed the cover and looked at it while watching. But I can determine a number of segments that it ISN'T. It obviously isn't Me, Claudias or Upstairs, Downstairs (because of the different sets), but I can also tell it's not Chariots of Fur, The Sound of Music (I'll be surprised if that gets a commercial release, since it not only uses a licensed song, but a licensed version of that song), The 39 Stairs, or The Horse Whisperer. But we've only got two more months and a week.
I did notice that each segment with stills on the cover is represented with three images each. But we get three images from The King and I and three images of Alistair Cookie, which either means it has more than one Mosnterpiece Theater sketch (which it should), or that one sketch is the only one represented with more than three images.
Another thing I noticed: The cover has four rows of "filmstrips" with still images. The two in the center only show images from clips shot in HD, while the two strips on the end show full frame clips. I guess that is a wise choice.
I was saying previously that I hope this leads to a trend of two-disc releases, but the logo gives me a bit more hope. At the top, it says "Best of Sesame Street", with "Best of" above the usual Sesame Street logo, and "Spoofs! Vols. 1 and 2" below. On the spine, we see the Sesame Street logo, and next to that just "Spoofs Vols. 1 and 2". No "best of" on the spine, and the Sesame Street logo is pretty much always on a DVD spine, making it look like the title is just "Spoofs!". This looks like a good possiblility, annual or twice-annual two-disc "Best of Sesame Street" releases. I hope I'm right in my predictions.