Excellent. This would be a good resource for those participating in the banner contest. Why unequal dimensions?

My only suggestion would be to make the coin's text stand out more. At tiny resolutions outlines tend to be come unworkable, so a better option may be to experiment with contrast. Making the text significantly darker than the rest of the coin would likely increase readability. Alternately, you could make the inner circle color darker, and the text lighter.