some excerpts from the policy:

• Images must be realistically useful for an educational purpose

• From policy section on legitimate use: Not all images for example are realistically useful for an educational purpose. An image does not magically become useful by virtue of the argument that it could be used to illustrate a Wikipedia article on X, merely because X happens to be the subject of the photograph.

• From project scope discussion:

New and existing files of poor or mediocre quality may or may not be realistically useful for an educational purpose depending on what they illustrate and what other files we have of the same subject.

...there is no purpose in our hosting many essentially identical poor-quality images that have no realistic educational value.