One of the things I like on perlmonks is the plain structure of the site. No (flashing) images on top, left or right, only two colors (as defined in the theme I use) (except that very decent one pair-advertisement and the lone monk to the right). That way I find it very easy to concentrate on the important things (the content).

The example picture you provided is too big and too colorful for my taste. I don't see any benefit of that picture vs. a written advice to use strict and warnings. And why should I believe what a dog tells me???

But probably my taste is too old-fashioned.

So go ahead with that change if you think it improves the place. But don't forget to implement the feature I like most in your proposal: the ability to turn the pictures off.