Something else I thought of tonight: Maybe an official photo (meaning not a screenshot) on the front, and a few still images from classic stills on the back, maybe with text overlayed on it.
Or maybe five images on the front: Four square clockwise still shots from the show, and a circular image that's not a still. For example, the Grover card could have stills from his "Near and Far" sketch, a Super-Grover segment, a waiter Grover segment, and Monster in the Mirror (or maybe an image of the original green Grover could be pictured in place of Monster in the Mirror or "near and far", maybe even the original "near and far" sketch). The Cookie Monster one could have images from the original C is for Cookie, Allistair Cookie, one of the Cookie's Crumby Pictures segments, and The Cookie Bunny. For Ernie, there could be images from the season two "Rubber Duckie", Ernie with a banana in his ear, "Dance Myself to Sleep" (or "I Don't Want to Live on the Moon"), and Ernie as a knight from "Imagine That". For Bert, images could be from "Doin' the Pigeon", "Bert's Blanket", Ernie putting a pan on Bert's head, and Bert teaching Bernice how to play checkers. For Elmo, include images form "One Fine Face", "Elmo's Song", an Elmo's World clip, and an Elmo The Musical! clip. For someone more obscure like Bruno, include images from "Put It in the Trash Can", "bring your own can night", "Trash Outta Heaven", and Bruno on roller skates from "Big Bird's Birthday".
I also wonder if it'd be good to have different scarcity on each card. Maybe not something really scarce (like a card that only appears in 1 out of every 10 packages), but maybe the most common cards could have a 6 out of 10 chance of being in the package, and the least common being 3 out of 10. And when it comes to most common and least common cards, I wonder if it'd be better for the most popular characters being on the most common cards or least (and vice versa). Any idea which is more common for collectible trading cards for popular franchises? But in my mind, I'd have the Big Bird, Elmo, Abby, Cookie Monster, and The Count cards have a 6 out of 10 chance of being included, Ernie, Bert, Grover, Guy Smiley, Biff and Sully, Oscar, Slimey, and Zoe a 5 out of 10 chance, the Baby Bear, Telly, Herry, Prairie Dawn, Forgetful Jones, Clementine, Buster, Gladys, Rosita, Murray, Snuffy, and Two-Headed Monster cards a 4 out of 10 chance, and everybody else a 3 out of 10 chance.
I didn't include him on my previous list of characters, but I wonder if Sesame Workshop could include Kermit in a collection of Sesame Street trading cards. I'd like to think it's as okay as including existing Kermit material on video, online, album releases, and books on the history of the show, but you never know. Maybe that one could be a "special edition rare card", with only 1 or 2 included in every 10 packages. Though if a Kermit card could be included, and the card collection used my idea of screen shots around a non-still image, then perhaps many of the other character cards could have images from skits Kermit appeared in with them (like the Grover and Cookie ones having stills from one of the many Kermit and Grover/Cookie skits, and appearances alongside Kermit can appear on the cards for Don Music, Dr. Nobel Price, and Forgetful Jones, and so on). And still images I would choose for the Kermit card would be from the original "Bein' Green", Kermit's interview with Humpty Dumpty, Kermit and Joey singing the alphabet, and a Kermit and Grover skit.
Thinking more about my trading card idea, maybe for the 45th anniversary there could be 45 character cards, and then after the anniversary maybe a wave 2 or additional cards (maybe some characters could replace previous characters). There are a lot of characters I left out that I shouldn't have, like The Amazing Mumford, Chrissy and the Alphabeats, Little Jerry and the Monotones, Harvey Kneeslapper, Simon Soundman, Roxy Marie, Hoots the Owl, Fred the Wonder Horse, and of course many more!