Open your favorite search engine and select the "Image" search. Type in the name of the movie and press "Enter." All of the available images will appear, with the resolution underneath. The larger the image resolution, the better the picture quality is. Download the image by right-clicking the file. Choose "Save Pictures As," then choose a location to save the file to and click "OK."
Navigate to IMDb.com. Type in the name of the movie into the search bar, then press "Enter." Along the top of the page are all the available stills from the movie.
Go to the movie's main website (most movies now have their own web page). Check for a "Downloads" option, as many offer free downloads for your computer. Click the "Download" link next to the image you want, and the picture will download to your computer system.