Solution: Google image search
Here's how to find the picture, assuming you have Google Chrome:
1. Put the picture you want to look for on your desktop
2. Go to images.google.com
3. Left click the icon for the picture and drag it into the box
4. Google will search for the image and give you results. Let's say I want to see that picture in a different size. I click on "All sizes" as shown below.
5. I get a results page with the same pic in lots of different sizes.