I've bitten the bullet and moved to completely designing my cards in Gimp for OS X. You should notice a change in the quality of the image.
Let me know if anything else stands out to you that needs improvement!
This card is a bit vanilla, so judge away on that as well!
The purpose of moving to Gimp is to be able to design new icons that should make for more interesting new cards, which I'll be working on right away.
Keep the comments coming!