Google's image search engine added an expandable toolbelt with search options that allow you to refine the results without visiting the advanced search page. Much like web search and Google Video, the image search engine exposes some options that were already available, but they were difficult to find.
You can pick the size by choosing medium, large, icon, by specifying the exact size or by selecting "larger than" and choosing one of the lower bounds. For example, you can restrict the results to images larger than 2 MP (1600x1200).
Other options include the type of image (face, photo, line drawing, clip art) and the colors (black and white, full color, predominantly red, predominantly blue etc.).
Let's find 2MP+ photos that are mostly gray and they include penguins.