To tweet pictures from your flickr account you can use flicktotwit sites.It's a nice service that allows integration between your twitter and flickr accounts. You can upload pictures to your flickr account from here, and give some text to go along. The text will automatically become a twitter update with a link to your photo. While you are linking the two accounts, be sure to complete the authorisation process carefully. Yahoo! will require you to authorise Flicktotwitt to access your flickr account. The other option for Firefox users is to use the Oickr2twilter add-on. This one too is similar in terms of functions.