WordPress: Adding media, custom alignment styles?

Hi guys,
I've been searching everywhere for a way to do this, but nobody seems to know how, so I thought I'd ask here!
Basically, when you add a new image to an article in WordPress, you can choose from 3 alignment options: left, right and center.
I want to be able to add 2 new extra styles, with their own css classes associated. I can't just repurpose the css for the current selectors, as I want these in addition.
Does anyone know a good or even hacky way to do this? Thanks!…
WordPress: Adding media, custom alignment styles?

See original post by Josh-H