Now you can add a picture or photo to your tweet directly from Twitter.com. Twitter introduced the notion of attachment to its Web service. You can see the camera icon of under the tweet field. When you click on this icon, you can attach a picture to your tweet. Once uploaded, the thumbnail of your photo will appear below your message. If an error occurs, you can click the X that appears in the upper right corner of the image to remove it.
After you attach your picture, the camera icon will turn blue and your picture will show up, scaled down, in the bottom left corner of your tweet box.
The maximum size of an image attached to a tweet is 3Mb. If you have a private account, only those who follow you will see your photos. In a few weeks, all accounts will have access to their picture gallery.
Previously, users had to use services like Twitpic, Lockerz or Flickr. You will still be able to use these services and view other images from these services. Also now you can add your loaction to your tweet with location sharing service from twitter.
This is a cool feature from twitter. Though it will kill services like twitpic, yfrog, etc!!