TinEye is a reverse image search engine. You upload your image, and TinEye attempts to match it to one in their database. If it succeeds, you have a name to go with the picture. For example, it correctly identified a young Sarah Palin for me from this picture, but came up with zero for David Orchard and this guy (who is actually quite famous: guess his name and you win some imaginary steak knives). Might be a worthwhile tool when their image database gets bigger. But since the point is usually to put a name to the picture of some obscurity, TinEye isn't there yet.
Not sure what the difference between TinEye and running a images file-name through google is.