An inspirational poster can really inspire us!
Its benefits to us are based on scientific principles of how our minds work. Almost every inspirational poster has both images and words. Once in a while, one may just have words, but when that happens, the words are usually done in a very artistic way.
Different parts of our minds respond to words and to images: generally, the left side of the brain is more logical and word-oriented, while the right side of the brain is more global and image-oriented. So an inspirational poster can easily speak to us in two different ways.
Another principle that allows inspirational posters to help us is that of repetition. The more we are exposed to something, the more it can affect us. Advertising works on this principle, but here we're talking about how we can use posters to help ourselves. When you get a new poster, at first you may stop and look at it a lot, but over time you become more accustomed to it and probably pay less attention to it. But even when you walk by it and glance at it with your mind totally on other things, the message of the inspirational poster is registering in your mind.
An amusing example of this once happened to my sister-in-law. Someone gave her and her husband an attractive poster that said something like "Caribbean Vacation" on the bottom and had a photograph of a beach scene. She put it up in a hallway in their house. A few months later, they happened to win a one-week vacation to a Caribbean island. Everyone laughed about the coincidence, but I guessed that it might have been more than just coincidence. They had a great trip, by the way.
Inspirational posters come in a variety of themes. Many draw on images of physical courage, while others have a more spiritual or religious message. I suppose you could call them motivational posters. And who couldn't use more inspiration?
Rosana Hart writes about many popular poster categories at her website http://www.infoandhelp.com/posters/ and a selection of inspirational and motivational posters can be seen there.