I don't know, but I suspect that many of the images that are PD-UK would be useable under fair use in the USA. If so would it be possible to use a dual licesnse along the lines of "This images is public domain in the United Kingdom and other countries that use death+70. In the United States this image is contended to be fair use because of xyz" ?
Images are never "fair use" on their own. Specific uses may be fair, for *any* image. There's no such thing as a collection of fair use images, by definition.
-- Daniel