The promoted pawn in the center has a larger character than the one at f2. Personally, I think f2 looks better. Please compare this with the gold piece on e4. They match in size, but the other pieces seem to have a better look being bigger. I put a matching gold one at f5 for comparison. This would mean the promoted pawns would look a little smaller in size than the rest, but I don't think it will look off. It will be easier to determine if it's up and running.
I put up a light wooden background, but the color could be a default light color. What I was thinking to get the background wooden look with the 4 black circles, was to have an option in settings to choose a background image (people just browse their computer to select it). This could then be set as the background for the table. So, even if you don't like the background I have up (which I would like to tinker with more), you could always add your own. Also, I would like to see the table border color change from grey.
The background color of the pieces match the sides of the site. I have kept the border black look, but if I have time I'll see if I can enhance it a bit.