1. First go to Google Images.
2.Now type your Keyword and than type your dimension or size which you are searching like:
Natural Wallpapers 1024 X 728
|Natural Wallpapers 1024 X 728 Search In Google Images|
3.Change the “Natural Wallpapers” to your keyword and than change the “1024 X 728″ to your search term.
4.Finally you are done.