Many of the recent and not so recent postings on this topic start off
something like, "we are a small/medium/large museum and we want to put
our images on the Web, but we are worried about security..." and then
we go off on the high res/low res tangent again.  I think a more
important question is "why do you want to put your pictures on the
Web?" If it is just to get them up, then really all you are doing
is saying, "Here, look at this, and this, now this...." It can quickly
degenerate into a vaction slide show in which each slide takes 15-30
seconds to load.
There are two other possibilities which we use on our site
(http://www.indiana.edu/~mathers/home.html) and on my own
page
(http:/bronze.ucs.indiana.edu/~tkavanag/home.html):
catalogs and papers. One nice thing about the Web is that some basic
research can be done from the comfort of your own home. We have a collection
of some 8000+ photographs of American Indians taken between 1908 and 1923 which
we are working on getting on the Web. A partial listing is already up on our pag
e and we are working on making it searchable. On my own page, I have several
papers on "reading photographs" of American Indians, as well as catalogs
of the James Mooney photographs and of the Will Soule photographs.
Don't just put the pictures up, do something with them!
tk