Andy Chase

Drupal 5.x does not support HTML image inputs (<image type="input" src="…"/>) out of the box. A common solution to this limitation is to provide your own theming function to handle any buttons you want to turn into images, as described at http://drupal.org/node/144758.

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When digging around for Drupal Forms API examples make sure you know which version of Drupal the examples you find are for; the differences between 4.x and 5.x are just subtle enough so as to be terribly confusing.

Finally, I found this discussion thread. For a clear, functional example see the second comment down by pwolanin, “Wrong code above, and 2nd point: form_id”. The code works, and the explanation of how the form_id is named is tremendously helpful:

http://drupal.org/node/119117