Wait a minute. First, which poster is that an EXACT image from? I know Juli was using the same avatar for awhile. Second, it is a little bit hypocritical to say we own the image when it comes off a poster that clearly states it is owned by the NSS and not for sale. Even with expiration of copyright, many of the images from recent studio posters would still be piracy under this law.
My normal avatar is probably clean because it is pre-nss (1921) and I own the only known copy of that poster, but I am not feeling terribly secure. It still has Richard Dix' image on it, and the heirs might be protecting that, much the same way they aggressively protect images of Marilyn, James Dean and Elvis
as a whole, this issue needs to be answered by someone who is more expert in the area of copyright of which my knowledge ends at a certain level.
however as concerns the FP poster: this is part of an issue that was resolved more than 20 years ago and while the film producers in Hollywood in general correctly registered copyrights on the films themselves, they did not follow correct procedures in registering copyrights on all materials related to the films. One of these issues is a physical registration with the Library of Congress that required paperwork to be filed at a cost of (at the time) $20 or $25 per registration. Seeing as the companies did not view the paper as a "continuous use product" for later releases of the films, the need to pay $25 to properly copyright the poster has left the use of said images in the public domain for a vast majority of material prior to 1968. After that time, it was no longer necessary to register in such a fashion. This is why the posters can be used and why (for instance) whenever you see documentaries on movie stars, footage is captured from trailers which also were not (in general) registered, although trailers do have certain derivative copyright. Copyright renewals were subject to the same law until later law which revised these issues.
Ergo, the generally recognized cutoff is 1968.
Furthermore, Fair Use is what allows people, like Bruce and Heritage, to publish books reprinting these images without any royalty to the creators of the posters
there are also loads of films which lapsed into the public domain immediately upon release because no copyright filings were filed. This is why Films like Marijuana and Reefer Madness can be released and sold by anyone.
Later usage, as long as it is within the fair use doctrine - like some using an image from a Harry Potter poster for an avatar. What it means however is this: the studio can deny the ability to use that image by sending you a cease and desist, if they so choose, for any work they produced, however it does not mean that they can sue for $$. If you ignore the cease & desist, that's a different ballgame
Believe it or not, for those of you who are comic fans, very much of the Tower Comics' "Thunder Agents" publications of the 1960s are in the public domain, because no copyright filings were made for the majority of them. So both the characters and the comics can be freely reprinted or even new stories created. (there were specific lawsuits related to these publications about 20+ years ago)
today, copyright is attached the moment of creation. This was not the case before 1968.
I'm sure some of what I have written here is not 100% on target as though I have studied up on copyrights as part of a public domain issue as a publisher myself, which is why someone who is expert in this area would better be able to explain this issues.
Disney will sue anyone - whether or not the material in question remains under copyright or not. Their idea is to bury you in costs that negate the value of reproducing or reprinting their material. Seeing as lawsuits in the US do not prevent anyone from erroneously or vindictively filing on you and in failure - the law does not require you to reimbursed for your legal expenses by the unsuccessful plaintiff - this will continue.