The New York Times has four categories for the multimedia they use on their website: interactives, photography, videos and podcast. Photographs and videos almost always accompany front page and breaking news stories. Podcast and interactives are general used in opinion and filler stories.
The Washington Post has three main categories for their multimedia: photos/slideshows, videos and blogs. They use their blog section as a way to prompt discussion with their readers.
Both the New York Times and Washington Post use social media outlets like Facebook and Twitter, allowing readers to comment and repost their stories.
These uses of multimedia help to further tell the story by adding visual details and opportunity for people to discuss issues in a public forum.
What's a filler story?
Filler may not be the correct term. "Fluff" is the term we use when filling TV air time.
Here is what I was looking at when I was writing this post:
http://www.nytimes.com/interactive/2012/06/29/arts/music/build-a-pop-song.html?ref=multimedia#/?id=all
It is interactive. It isn't really news. Culture feature maybe?