Twitter has started image upload feature in profile header- Now in twitter you can upload images with tweets and can also add a header image for your profile.
Social networking sites continue adding many features to their pages to lure more users to add their network. Like facebook has started video chat, Google Plus has started Google Plus hangout for which you can do video conferencing between your circle friends.
And twitter has start to enable you desired images along with your tweets. Also twitter has start to add a picture in the header of your profile just like facebook time line header to attract their visitors. You can also send your tweets to facebook.