Flight Rising Trading Cards

Because I'm collecting Doctor Who Alien Attax cards at the moment, I thought, wouldn't it be fun to do Flight Rising on-line Trading Cards? Cards we could keep a site somewhere, or on a dragon's profile, and maybe start a game with.

We've already discussed some things in the Chat box down below.

Stats will probably be the stats the dragons will have on site, prehaps at different levels. Hatchlings will be lvl 1, then you can choose to have another or more cards of your dragons at say lvl 5, lvl 15, up to lvl 20 when they Max out.

There will also be a database of cards, just not sure where we will put them.

I am gonna need some help with this though.

Here is a basic doodle I did for the card's layout:
link

I was thinking of doing painted backgrounds for the different elements.
Size I was thinking of doing: 350x500
I was also thinking of doing them for free.

Questions:
Is the size acceptable? Should they be bigger/smaller?
Any ideas on the design?
Should there be rarities? should they be fully collectible? Or should they just be like an adoptable like thing?
If it's ok, should we use the site art, or do our own art for the dragons? (I was thinking of letting people also use their own fan art anyway, in special limited edition.)

Any views or opinions you have on these will be greatly appreciated, even if you are poo pooing the idea. Also any help on designs would be appreciated too.