Twitter today announced an image gallery and browser that makes it easy for you to browse all the images ever shared by any user (at least up to 100, and only back as far as January 1, 2010). It works in conjunction with a number of popular image sharing services, including Twitter, yFrog, TwitPic, Instagram and other image sharing services supported in Twitter's details pane.
The feature can be seen on any Twitter user profile. Near the top of the right column, you'll see up to four thumbnail images under the heading “Recent Images.” You can browse right from the profile screen by clicking the arrow buttons to scroll through the thumbnails (very similar to the interface on a Flickr photostream).
Clicking view all opens a lightbox with a gallery of thumbnails. Clicking any thumbnail opens a larger view, and clicking the larger view takes you to the source page (i.e. Instagram).
Your photos shared in public tweets are publicly browse-able, but you can remove them by deleting the original tweet with the link. Note that this won't remove the image from whatever service you originally shared it on.
So far, this feature is only available in the web version of Twitter. It's yet to be seen whether this will be rolled out in updates to their desktop and mobile apps.