Studio Ghibli releases 400 free-to-use images
You can bulk download these with wget like so;<p><pre><code>  wget http://www.ghibli.jp/gallery/{ged,chihiro,karigurashi,ponyo,kokurikozaka,marnie,kaguyahime,kazetachinu}{001..050}.jpg
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However they're low quality 1080p jpegs, so you're better off splitting out the frames of a blu-ray rip of the movie using ffmpeg or something.