The hashtag #JeSuisCharlie (I am Charlie) has been prevalent across a number of platforms. Given that so many of the dead were cartoonists and that blame for the incident was laid on a cartoon, it makes sense that a large portion of the tributes were visual.
Newspapers around the world used their front pages as a means of defiant protest against the attackers....
It's important to use social media for solidarity in a cause that matters to everyone. These media show how it's done.