If you’re not using IE7 compatibility mode, you can add some custom CSS (if your theme doesn’t allow this, try My Custom CSS plugin or any other plugin that allows adding custom css) to make the image less transparent. Here’s the line to add:
.pinit .pinit-overlay { background-color: rgba(255,255,255,0.9) !important; }
Change the 0.9 number (it ranges from 0.0 which will cause that the image won’t change on hover to 1.0, which will make the whole image white on hover, the default value is 0.5) to the desired value.
If you’re using IE7 compatibility mode, let me know, I’ll describe how to do this in that mode.
All in all, I’m planning on adding the possibility to change transparency level and (maybe) change the “Pin It” button image in the next version of the plugin.
If the given CSS does the job, let me know.