L5R has a long and proud tradition of using card ideas submitted by players. There are just a couple of simple rules. First, do not post card ideas in public. This means email lists, web forums, usenet, whatever. Anything posted publicly won't be used.
Second, send your card ideas directly to bkeith@alderac.com, with the following legal text filled in:
I, ______________, understand and agree to the following terms:
Unsolicited artwork, story lines, character developments and other intellectual property (collectively "work") received by AEG is considered a gift of all the donor's rights, title and interest in and to the Work (including copyright, trademark or other intellectual property rights) which Work is given to AEG for no consideration, and becomes the property of AEG. AEG is in no way responsible to pay any transfer fees, licensing fees, royalties or any other consideration to the donor. Based on the above understanding, I hereby submit the enclosed Work.