Indeed the popular solution by Jeremy Mansfield at www.brandaiddesignco.com has a great method to customize the Pinterest button any way you want!
I’ve made three examples, in the form of jsFiddle’s, so you can see how it’s done using that method.
Reference: jsFiddle Text-Link method
Reference: jsFiddle Custom Logo method
Reference: jsFiddle Custom Logo and Image method
For more Pinterest Info, see my other SO Answer.