There is an interesting story in the Washington Post by Susan D. Moeller noting the power photographs can have in moving public opinion. She sites specifically the Iwo Jima photograph which may be the most important war photograph ever. Ms Moeller notes that the image communicated that the US was winning the Pacific War at a time when the outcome was still, I believe, in doubt. The photographer, Joe Rosenthal, notes that 'World War II was the "good war.' And Americans were the liberators." A feel good picture for a feel good war, a war we had to win.
During the Vietnam War, there was a powerful photograph of a child who had torn off her burning clothes in the aftermath of a napalm attack in Saigon that may have had more influence than any 1,000 words I heard or read on the war. I talked to a veteran of that war who spent something like nine months at the border between North and South Vietnam, living in muddy trenches, about napalm being routinely used to drive back North Vietnamese trying to break through their lines. I asked if dieing from napalm burns was as horrible way to die as I imagined it was and he said, "Yes." He, of course, actually saw it happen. We worry about the effects of chemical weapons but no one worries about the use of napalm which is probably as bad as any chemical weapon. Napalm was the weapon of choice, along with grenades, in clearing out bunkers on South Pacific islands inhabited by Japanese soldiers. Bit I digress. The Pulitzer Prize winning Vietnam photo mentioned above was a feel bad picture of a feel bad war.
It is interesting to look at how it is that photographs have meaning. If you go back to my Blog on The Meaning of "Meaning," you will see that I make a crucial distinction between conventional meaning (literal meaning, more or less) and utterance significance, which is fundamentally dependant on context. We can say, for instance, that the utterance "Can you pass the salt?" has a conventional meaning in which it is an interrogative sentence for which, if taken literally, a "Yes" or "No" answer would be appropriate but would normally be used at a dinner table to request the salt. As such it has the significance of communicating a speaker desire that the addressee hand the salt to the speaker. In certain respects conventional meaning requires some reference to context -- who the referent of "you" is in that question/request would depend on context. Utterance significance depends on context in a much more fundamental way. This is also true of pictures. If you saw the Vietnam War photograph without knowing when or where or why it was taken, you would see horrified people running but would have no idea why the child has no clothes on and what sort of impact it might have had on viewers when it was published. For that you need context.
Photographs have something akin to conventional sentence meanings though there is no theory about how one should go about assigning a conventional meaning to a photograph. Any photograph can be thought of as a representation of some state of affairs (think "re-presentation of what was visible to the eye"). Had a reporter seen that state of affairs he or she might have described it verbally and this would be a verbal re-presentation of the visible state of affairs. It would take a very gifted writer to create a description that would match either of the photographs mentioned here in its impact.
The impact of a photograph is analogous to the significance of an utterance. The difference lies in the fact that there is no accepted theory of photograph interpretation analogous to the theories that have been proposed for how we interpret utterances. This is normally not an important consideration. Members of a family might sit around a bunch of family photos and talk about them in some informal way. No one ever says things like "Hey, you aren't supposed to interpret a photograph that way." There is no accepted way of interpreting photographs. Indeed, there is a very interesting description of the Thematic Apperception Test I suggest you may want to read in which psychiatrists or psychologists and others show photographs to people and ask them to describe what they are seeing. There wouldn't be such a test if people didn't differ a great deal in how they interpret photographs depending on their mental states or in the case of "normal" people on such factors as gender or race or culture.
There is one domain in which "objective" photographic interpretation becomes important and that is the law. Forensic photography is a critical aspect of crime detection because officers normally don't keep a crime scene open for repeat visits for very long and in some cases photographs can reveal things that the eye can't see, as when infrared photographs are used to document gunshot residue. Ultimately, what the detectives end up with is a bunch of photographs to study, the crime scene having long since been cleaned up. In this domain, methods of photographic interpretation become important. Naturally, of course, when a case goes to trial, the defense expert will tend to interpret the photographic evidence in the light most favorable to the defendant (without necessarily lying or obfuscating the facts) and the prosecution expert will offer the most incriminating interpretation of what the photograph shows.
Photographs are different from other sorts of graphic objects such as paintings, logos, and jewelry of various sorts. We think we know what a cross hanging from someone's neck "means" or what a swastika pin or tattoo "means" though the fact is that the "meanings" of such things can vary culturally. This is particularly true of the swastika. In some cases, when we see a piece of jewelry that is abstract in the way a swastika pin is, we suspect it has some significance. On CNN, the afternoon anchor said she ran across a guy wearing a pendant that she assumed had some significance but when she asked the guy what it meant he brushed her off. That afternoon she had a journalist on the show who had done research on "boy love" and "girl love" paedophiles and showed images of the "boy love" and "girl love" pendants paedophiles sometimes wear to communicate to others of their kind that they would welcome meeting them. The guy was wearing the "boy love" pendant.
So, I conclude this rambling post by saying that "No," a picture is not worth a thousand words both because but we can't really say what exact words would be equivalent to a picture and because in many cases no amount of words could have the impact of a picture. Indeed, I think poetry exists in part because ordinary language is inadequate to communicate feelings, emotions, and other important things. Indeed, we have coined the word "ineffable" for just such things.