I genuinely think that any of these could be considered, BUT I would say it has to be that it is in the image some way, for me to personally care for it as a cameo.
I think the collectors themselves set the boundaries but for me personally i should be able to see the Pokemon on the card in some capacity atleast. So for me, artbox and logo makes it a cameo.
Good question but your stamp example feels more open. Would you consider this a Raichu card? It is a tiny alolan Raichu. I have not counted those as I want to actually grade all 10’s one day and adding in two half deck worth of little stamps feels overkill even to my Raichu loving brain.
Given I accept this as a raichu shadow I have been all about the art box. With a stamp as nice as OP’s example I probably would have counted that but not a deck list tiny symbol.
I’m not a species/cameo collector however, if I was I think I’d draw the line with artwork box and stamp logo. I think that’s the majority vote.
I respect anyone’s decision and dedication who thinks to go for every reference although, I think that’s more of an Easter egg and not specifically a cameo.
Results are about as expected:
100% for the Pokemon being featured in the artwork. Thank you for everyone taking this seriously and actually voting for this one.
~50% for being featured in the Pokemon Center logo stamp or promo stamp. Very cool to see e4 split 50/50 on something. Most of the time we are split more like 80/20 or 90/10 on topics.
14% for having a tiny logo stamp in the bottom corner of the card for being a theme deck. In my example of Sylveon, the stamp is unique to the deck, can’t find that silhouette anywhere else.
7% if the name is in the effect text of the card. Obviously not an art cameo, but the card was made for playability specifically for that Pokemon, so it’s cool atleast.
I go for the name on the card. But mainly because the one card that does it, is Sylveon themed in colors, and it’s obviously the Sylveon Ribbon. Honestly, not sure if I’d consider it part of the collection if the artwork wasn’t basically Sylveon in a badge form.
Personally, I think they all are cameos. What matters to me and my specific overall collection focus is if PSA will recognize it to add it to their Master Set Registry. Which generally, precludes all cameos. While in the long run, this saves me a ton of money not having to grade them all. I still like to have them.
Like the Gyarados EX in BreakPoint (I do have all 3 versions of this one graded, but that’s because I really like this one);
Or all the Greninja ex & Darkrai ex Battle Academy Deck cards that have a Greninja stamp on them;