re. Snowfall's screenshot (moved from Gallery thread)
 

I'm an avid WA user, and I could have sworn it was possible to create icon elements and make them clickable. I could be thinking of another addon. I'm at work now and can't confirm til I get home later, apologies.

Regardless of whether or not WA itself will let you make clickable buttons, the main issue is what you want the button to do when clicked.

It's not possible to have a WA button that casts a spell when clicked, for example -- in order to cast a spell when clicked, you need a secure action button, and WA doesn't do that.

Even if WA did make secure action buttons, they would lose the standard WA functionality of being able to appear and disappear based on arbitrary conditions -- you can only hide or show a secure action button based on the same conditions you can check for in a macro, so you would not be able to show the icon when your trinket procced, when the ability came off cooldown, when your target's health fell below 20%, etc.

See also the "Things Addons/Macros Can't Do" sticky thread. You'll be most interested in the section about "secure/protected actions".