We have seen number of Google search refinement options (& operators) for specific results. Like searching for only PDF ebooks or using Google Image search to only show face images. Here is another image search refinement option based on size of image.
You can specify size of images you want related to specific keyword. For example if you want wallpaper sized (1024X768) images of fireworks visuals then search for imagesize:1024×768 fireworks on Google Image Search. You can change size values and keyword as per requirement. [via]