Make sure the images is centered, but use as much horisontal width as possible. Take 1.
How to remove white-space space in between UI/UX elements.
Enable styling the <select> the way you want by replacing it with a HTML variant. Changes in the HTML variant is reflected in the <select> (which now is hidden), so this should work in existing forms.
Use a discrete model to sample the value of Pi, instead of random samping.
Someone asked me if you could animate changing the src-attribute on the img-tag. I gave him t his.
Just a quick example to see what I come up with given little time.
See how keyboard and mouse-events behave.