Our county WIC office took pictures of some of their clients
breastfeeding--the one I remember is of a couple of families at a local park,
with dads and toddlers as well as nursing babies, I think.  I don't know if
they'd share these or maybe sell them.  I can't remember who posted the
question originally, but if you'd like for me to check, e-mail me privately.
(The humorous ones from Canada are great, too, but they aren't of nursing
dyads in public places.)

Judy D in WV