We used the simpliepie library to access the Twitter API recently and ran in to an issue trying to access the image link field from the XML.
This is the image link that gives you a direct link to the twitter users profile picture.
Using the get_link() function would only return the link to the users profile. After reading the API manual we used:
<?php echo $item->get_link(0, 'image'); >
And our problem was solved.