The acidfree module provides an acidfree filter so that you can add acidfree images to other nodes

[acidfree:732] will add the image in node 732 to the current node. It has class "acidfree-plain" and links to the image node.

The lightbox2 automatic image handling does not recognize these images as acidfree images and thus clicking on the image brings you to image node. If I add acidfree-plain as a custom image class, lightbox2 attempts can't figure out what image to load in the lightbox and displays an error image.