The cels that still exist today were saved by the animators and producers themselves, often given away as gifts and promotional material. The Disney studio, for example, would offer them for cheap sale at Disneyland. Leon Schlesinger signed them and gave them out. Tex Avery recalled giving cels to local kids. Mel Blanc used them to sign autographs. As evidenced by a couple of the cels I'm presenting here, animator Virgil Ross would sign them and give them as gifts. So they ARE out there, and while they fetch thousands of dollars on the collectors' market today, they're an incredible glimpse into the history of animation...and thankfully, photos of them on the internet don't cost a dime!
Cel from "Johnny Smith and Poker-Huntas" (Tex Avery, 1938).
Cel from "The Hair Brained Hypnotist" (Friz Freleng, 1942)
Cel from "My Bunny Lies Over the Sea" (Chuck Jones, 1948).
Cel from "The Cat's Bah" ( Chuck Jones, 1954).
Cel of the Road Runner from "Zipping Along" (Chuck Jones, 1953)*.(Possibly misidentified. This looks to be from a later Jones short. the Roadrunner became more streamlined as time went on, and "Zipping Along" features a more detailed, earlier design.)
* Confirming my suspicion is cartoon expert Chase Pritchard, who identified this cel as being from "Rushing Roulette", a Robert McKimson cartoon from 1965. Here's a frame from the actual cartoon to prove it. Good eye, Chase! (the background, on the other hand, is definitely from a '50's Jones effort.
Cel from "To Hare is Human" ( Chuck Jones,1956). Signed by Mel Blanc!
Cel from "Jumpin' Jupiter" (Chuck Jones, 1955).
Cel from "The High and the Flighty" (Robert McKimson, 1956).
Cel from "Greedy For Tweety" (Friz Freleng, 1957).
Cel of Miss Prissy from "Of Rice and Hen" ( Robert McKimson,1953) paired with a cel of Foghorn Leghorn from "Weasel While you Work" (McKimson, 1958).
Cel of Sylvester from a 1950's McKimson Hippety Hopper short. * Thanks to the keen eye of reader Matthew Yorston, we know that this cel comes from "Lighthouse Mouse" (Robert McKimson, 1955).
* Here's the frame from the actual cartoon to prove it. Thanks, Matthew!
Cel from "West of the Pesos" (Robert McKimson, 1960).
Cel from "Trip For Tat" (Friz Freleng, 1960).
Cels of Bugs Bunny and Daffy Duck from "The Bugs Bunny Show" (Circa 1961). Note the Daffy Cel: Heads and bodies were often painted on separate cels in later years to save time and money.
Cel of Sylvester Junior from "Birds of a Father" (Robert McKimson, 1961).
Cel from "A Sheep In the Deep" (Chuck Jones, 1962).
Cel from "Adventures of the Road Runner" (Chuck Jones, 1962).
Cel from "Louvre Come Back To Me" (Chuck Jones, 1962).
Cel from "Mexican Cat Dance" (1963).
Cel from "Dr. Devil and Mister Hare" ( Robert McKimson, 1964).
Cel of the Road Runner disguised as Wile E. Coyote, from a 'Road Runner Show" TV bumper directed by Robert McKimson, circa 1965.
Cel of Wile E. Coyote from an unidentified 1960's cartoon short.
A pair of Daffy Duck cels from a Robert McKimson Daffy/Speedy Gonzales short, mid to late 1960's. * Thanks again to the keen eye of Chase Pritchard, we know these cels come from "A Taste of Catnip" (McKimson, 1966). Frames included below for comparison. Notice that the second cel is missing Daffy's bill...it was animated on a separate cel.