I have been trying to find images on the web that will match images that I upload and I have come across a few cool websites.
To start with there is pixolu. Although it doesn't enable you to upload an image, it lets you search for particular key words and then select the types of images that you would like. Using these images, it then refines the search to find images similar to those that you have selected. I thought it was a very nifty tool. This is quite similar to Google Similar Image, except that it has a nicer interface and a lot of images in the Google Similar don't actually have a similar even though the same image in pixolu does.
Then there is retrievr which still doesn't let you upload an image but you can squiggle something in a box an it will find similar images on the web. I was impressed to find that when I did a very rough drawing of a tulip, the search did pull up an image of a tulip (see the screenshot).
But something like Gazopa was what I was really looking for. Unfortunately, it doesn't work as well as I would hope. Even though the image I upload is available on Flickr, it doesn't actually find it. It does do a good job at finding images with similar colours (see screenshot).