If you think you can do a better job, then definitely post an example of your card design. The guild mods will pick out the best design.
Your design will be used on every card until possibly a better design comes along, but don't worry, we'll keep all the designs we have ever used. Also, your username will be printed on every card of your design.
Keep in mind that the guild colors are green and gold.(I know that's orange)
And please keep the size about the same as what we have now. Not too big and not too small.
Also, you can make your own guild official seal to go with your design.