The problem overlaps somewhat with the problem of including images in templates, when those images are not truly free in every sense. For instance, consider the popular user boxes that are cropping up all over the place (for some examples, see [[User:NSR/userboxes]]). Many of these include images that are tagged as fair use.
When images first started being used in templates, the images were all freely licensed or public domain. Because people editing a template do not control how other people will use it, I do not think it is appropriate to add a "fair use" image to any template. Since legitimately claiming fair use depends on considering the nature of each use separately, I find it virtually impossible that they could say with any confidence that all of the resulting uses qualify as fair.
--Michael Snow