Where are the post photos?
Usually the photos are linked to or shown with the post when you view a post on the site.
But some people access the groups from the Yahoo Groups site which has a photo section.
Sadly, photos uploaded to Yahoo Groups are only accessible if you have an account there.
So you can either re-join the group the post was from on the Yahoo Groups site (see links to Yahoo Groups) or it might be easier to just email the person and ask them to send you the photos.