fringe-helper.el contains helper functions for fringe bitmaps.
fringe-helper-define allows you to to define fringe bitmaps using a visual string replesentation. For example:
(fringe-helper-define 'test-bitmap '(top repeat)
It contains a few stock fringe bitmaps and helps taking care of creating and inserting them.
This looks extremely useful. Fringes are clearly under-used. Perhaps hideshowvis.el can use it to display +/- markers on foldable regions (more easily)?
See also, rfringe, which allows the use of the fringe for indicating buffer-relative positions. --DinoChiesa, 5 April 2011