We can use box-shadow and border-image inside background-image, we can use there outline, and even transform. We can rotate CSS Gradients and even rotate a bunch of gradients at once!
Better view in Chrome/Opera, transforms inside backgrounds don't work for CSS gradients in Firefox. And I didn't test demos in IE.
A common principle:
Look into a code for more details.
Аrticle in Russian: http://css.yoksel.ru/inline-styles-in-background/
Need to know how to enable it? Go here.