Just going to throw the most important thing out there now: YOU CAN MAKE AND SEND IN CARDS AT ANY TIME AND THEY CAN SHOW UP IN ANY GAME, REGARDLESS OF WHEN THEY WERE MADE. Think of the deck like a big pile of cards somewhere-people can throw cards in at any point and you can take cards from it at any point. Simples. Now, there are a few things to consider when making cards.
Firstly, the size of the card. These cards need to be 240 * 320 pixels EXACTLY. No more, no less. For the lazy among us, here's a template.
Now you literally have no excuse to mess with the sizes. Seriously, one pixel off and I'm just going to go nope.avi. Anyway, while it is not 100% required, most cards have a title for them to be referred to-however, as long as it's instantly identifiable, the subject of the card can also be used-for instance, a red love heart in the middle of a card with As in opposite corners can instantly be declared the Ace of Hearts. Make it identifiable!
Most cards also have some form of artwork on them. This can be as horrific as you want it to be. Seriously, it can even be something you just ripped off the internet. It doesn't even need to exist, but it's nice to put a BIT of effort in.
Some of the cards will be used for attacking and such-they need BOTH some number for Attack and Hearts. It can be incorrectly spelt, drawn as images, abbreviated-I don't care, as long as it's clear and both are present. Or neither. One on it's own will be ignored. If you want something to just be used for defensive purposes, give it 0 Attack. Something with 0 Hearts explodes instantly, so it doesn't really work the other way.
Now, almost all of the cards will have some form of effect. What should they do? I leave that to your imagination, but there are a few restrictions just so shit doesn't fly off the handle.
1) No insta-win/insta-loss cards. I don't mind if you want to make cards that make you win/lose, but they need to have a reasonable chance of cocking up, to be judged by me on a case by case basis.
2) Cards CAN affect other games, however, these effects can only be one-offs and cannot repeatedly affect the game unless the card is somehow re-played.
3) No Invincible cards. All cards have to be defeatable by some means that aren't card specific. I don't mind "This card cannot be destroyed by card effects" if I can punch it out with an Attack, but "This card can only be destroyed by XXX card" is stupid.
4) Cards can't forcibly set someone to below 0 points. It's alright if it would situationally happen, but nothing like "You now have -100 points"
5) Cards can't ridiculously outlive their time on the field. It's alright to have something that activates a few turns after the card leaves the field, but once a card is gone, it should be... well... gone.
6) If a card has illegible, incomprehensible or non-english effects, they are nulled.
Here are some I made earlier.
Once you've made some cards, send them to me IN A PM and I'll put them in the deckpile. Simple.