The service Google Images used to have a very useful "search by size" option in advanced search to help you find logos, wallpapers and other images on the Internet with their exact size (or resolution).
For example, you could limit your search to horizontal photos to image files at least 10 Megapixels in size.
Alternatively, if you use its Image Search Google to find desktop wallpapers, you could specify the image resolution as 1920 × 1080 pixels and the Google would return large images only with these exact dimensions.
The "exact size" search option is no longer available in its Image Search Google, but you can still specify the size of the images in your searches, using a command for the search algorithm.
Open the address images.google.com and enter the search terms as you always did. Then add imageize: LENGTH to your query and press Enter. THE Google will read the additional command in the query, remove it, but the results will only display images that match the specified size.
This resize search also works in its version Google for mobile phones. So you can use this simple trick to find the perfect wallpaper size for your phone.