At our last meeting, Karen mentioned that the dimensions she uses for submitting to the Copyright office are: 600 pixels on the LONGES adge at 72 dpi, using a size 8 resolution.
Here is an article that expands on it from Photoshelter (from 2009):
http://blog.photoshelter.com/2009/05/electronic-copyright-registrat/
Thanks,
JA
