Pics and videos are what tumblr is all about, along with posts that have no prayer of fitting in Twitter, much like this post. I love tumblr as an accessory to Twitter. I post deep stuff about myself here, and sometimes it includes pics or videos that help explain who I am to my twitter followers who are either kind enough to follow me here as well, or just kind enough to click on the link in the twitter post.
For stuff that I think is not for my average follower here or on twitter, I post the heavy stuff on http://un1k3n.blogspot.com/. I don’t post there too often, but when I do it’s the stuff that may alienate some of my followers here and on twitter.
But back to the point, tumblr without pictures wouldn’t be tumblr. This is where we can share things like that without worrying about too many links from twitter (yes, I know new twitter is better with pics and vids and stuff, but I’m just not used to it yet — even when a compatible pic/vid shows up on my timeline, I still click the link to see it where it was posted).