Use of old posters in a presentation

[rowan_m]

I'm going to be giving a talk at a conference and I'd like to use some classic sci-fi / horror movie posters in it. I've found several that are now public domain, which is great - however, I'm not sure about the others.

Specifically, the poster for "Return of the Fly" (search on google for the image, I'm a new member so can't post a link) from 1959 on which I want to alter the text for the presentation's title.

I'm not being paid for this conference, though the attendees are paying to attend.

So, my question is - am I allowed to make use of these posters?