I have a premium shop that I'm slowly working on customizing. (I'm a photographer, not a web designer so this is new to me) Is there a maximum or optimal size for a header/banner?
I've found the 500x200 limit for CP hosted logo images, but not for images hosted on photobucket etc.
I like yours without a header personally, but if you want one, I usually restrict header images to no more than 150 in height and whatever the width of the page is. I think yours would be around 800 px wide. You also have to consider what the purpose of the header is and what the tradeoffs are. If you're putting your "brand" on your shop, fine, but not at the expense of 5 extra seconds to download a 400k header graphic. You should try to keep the file size under 30-40k if you can. Smaller is better.