GazoPa, a similar image search engine developed by Hitachi America, is now open for public beta testing. You don't need a login. Simply go to GazoPa.com and check it out.
What you do is either upload an image, paste the URL to an image, type in a keyword - or even draw an image directly on the site. GazoPa will then try to find images similar to what you've provided.
Drawing an image was tempting, so I digitally sketched up a quick pumpkin, but it didn't exactly recognize the image. Hey, it's still in beta :)
Typing in pumpkin for a keyword search had me wondering if they had indexed any pumpkin images at all yet.
Next, I tried using a URL for a pumpkin photo from Flickr. Note that you need the actual URL of the image, not the URL for the page for the image on Flickr or whatever site you're using.
The results showed images with the similar color of the pumpkin, but not so many actual pumpkins.
To be thorough, I conducted other searches such as "pie," "cat," and "coffee," but the results were similar. There were at least felines included in the results for "cat," but I would expect more from an image search.
GazoPa seems to have similar color down, but needs to keep working on the Holy Grail of similar image subject. It's smart that they're opening it to a login-free public beta test. Those really interested in the advancement of image search will want to assist in helping GazoPa further innovate its offering.