Does the link also have the trailers that were used for the other movie's film card sets? I'd love to know what images were used for each film card set and what combo is even possible.
If use the link to for Yahoo Movies, you can type "Harry Potter" in the search engine and it'll pull up the other movies. Click on one and then look at the column on the left. You can click on "Trailers and Clips" to see them.

Generally, Artbox uses the teaser or theatrical trailer for the filmcards, but not the same trailer for both the first set and the update. I think there was one set that used the international trailer, but I can't remember which one.
I followed your link over to your POAU filmcard set and you have a great collection! Is there even an image that would go with Harry in Hogwart's courtyard?
Thanks! The only cells that match the courtyard filmcard are the exact courtyard cells. I've seen the cells twice in other cards.
It is 35mm Card Snape and Harry meet with the Marauders Map from POAU and the cell is an image of Snape. I have no idea if it is the hallway scene or not but I decided to buy it. That card is in the mail, maybe when it gets here I can figure out what it is.
The Leaky Cauldron, Mugglenet, and Veritaserum sites all have image galleries with screencaps from the trailers and movies. When you receive the Snape filmcard, you should be able to look at the screencaps and match what you have. The card you bought could have cells of Snape in the dark hallway, Snape walking into the DADA classroom, or Boggart Snape in Lupin's classroom.
My first film card I have in person and I love it. It is Harry in the Chamber from COS. The cell is over the shoulder of Riddle looking down at a CU of Harry as Riddle is pushing Harry's hair with a wand to show Harry's scar.
I don't recall seeing cells of Riddle in the COS cards, so you might have something rare!

Is there a section of the forum for discussing Harry Potter cards in general? Like do we know if the actors that played Snape and Hagrid have been asked to sign? Once the films are complete do we have any idea of how many other sets are planned? Has Warner Bros ever approved sketch cards for any of their other properties? Things like that.

Like Roz said, we usually talk about auto/costume/prop possibilities for whatever set is up next, in that particular section of the forum. We've had lots of discussions about Snape and Hagrid autos.

My guess is that since we haven't seen either auto yet, it probably means that Alan Rickman and Robbie Coltrane aren't interested in signing. I've read that Coltrane will not sign for any set, because he doesn't like the idea of people paying for his autograph.
Once the movies are done and the Deathly Hallows update set has been released, I'd bet my last dollar that Artbox will have many more sets planned. They won't reveal that info -- they still haven't released any info for OOTPU and that's coming out in mid-December.

We've already seen Memorable Moments and World of Harry Potter 3D. I don't think any of us will be surprised to see MM2 and World 2 after the last movie. Inkworks produces the Buffy the Vampire Slayer sets and Rittenhouse produces the Star Trek sets. Both franchises stopped producing TV shows a while ago, yet the card companies keep finding items for new sets. It'll be the same way with Artbox and Harry Potter.
There was talk of an HP sketch set last spring. A lot of the usual sketch card artists were asked to submit samples, but the project doesn't seem to be going anywhere. Some of the artists posted their samples on the Scoundrel website and one artist, Chris Henderson, has some of his samples in his eBay store.