I can find sites with galleries of early playing card designs, but are there any sites with galleries of more contemporary/custom designs? (The glut of personalized card deck printing companies is making this hard to search for.) I know of the Playing Card Collector's blog, but that has mostly relatively recent releases, and I'm looking for something more gallery-like anyway.
Playingcards.wikidot.com is a good place to start. It's incomplete, infrequently updated and far out of date, but the information it does possess is a treasure trove to the beginning collector.
52cartes.wordpress.com mentions what's up-and-coming and recently released, with some nice photography - and Google Translate doesn't do too bad a job of converting the French to English.
The archive at LoopCuts.com isn't a bad resource, either, though it's a bit short on data, focusing more on the photography and the ad copy from when the decks were released.
Searches on Kickstarter for "playing cards" and "deck cards" will pull up a large variety of deck projects - successful and not-so-much - that serves as sort of a gallery for the little guys of the deck publishing world.
Barring that, I could ask my wife about inviting you over to see my collection!
I currently have over 500 varieties of playing cards and about 1500+ decks. They fit in a surprisingly small space... The majority of my collection is recent releases, with a small but growing number of vintage decks going back as far as 100 years old.