First a few ideas on size ...
Thumb size : 150 x 200
Original size : 300 x 400
I'm thinking 300px should be a good width. Trying to fit an image into a 200x200 container is a major pain...
And 400px should be a reasonable height. Leaves enough space to add a caption at the bottom.
Each card will have the following info :
1. an image
2. a caption ( KAGAMI - Shrine Maiden, in this case )
3. rarity ( A,B,C,D,E,F,S,SS,SSS )
4. collection name
5. card what of what ( 1 of 12 )
The image itself should probably contain this information. Then we can enter it into a database along with the card.
This is going to be a HUGE project. I'm just taking stabs at things that'll move it ahead.
I believe it was Akikojam to first request. ^^
Anyone who asks "Will there be a battle system" must first show me code for a working game they wrote themselves.

All I plan to code is a simple card collecting game. Members create cards, and build a collection. Those collections can then be approved, and will be added to treasure chests as random loot. Once cards are found, you can collect them, trade them, or sell theme in a bazaar.
Feel free to post thoughts, questions and ideas that might help with moving this project forward and/or making it more awesome. ^_^
ALSO! Post some cards! I need images I can test.
[ Edited Jul 27, 2012 ]