Bicycle playing cards are all subtly different, depending on the size of the deck. For example, the Jack of Spades in the bridge sized deck is slightly different than the Jack of Spades in the standard sized deck. And there is at least one other deck size that is different from the bridge or standard sized decks. I noticed this when I accidentally replaced a bridge size deck with a standard size deck. Tonight I was looking at an LOLCat that was laying on some Bicycle playing cards and I decided "I'm going to figure out what sized deck that is." So I got my 2 decks and it was different from both of them. It was closest to the bridge size deck but there was subtle but definite difference in the pattern at the center of the Jack of Spades chest.
The person who answers questions for Bicycle playing cards' Facebook page is completely unaware of any of this. I asked in case there was maybe some interesting obscure trivial reason for it and they were just "it's just a difference in scaling when the image is stretched for the difference in card dimensions." and I'm like "no it isn't. The mace/scepter he's holding on the bridge deck has red accents that are missing on the standard deck. His robe has spades in the design on the bridge deck that are missing from the standard deck." That was the last I heard from them.
My conclusion is, Bicycle has been making playing cards since...1885, apparently. Back in the days before digital printing, even before photo lithography, artists had to create a different deck of art for each different size of cards. As the technology changed, they just kept using the original artwork as the basis for newer decks. I can't prove that, but it's the theory that fits the facts.