This snippet uses the video ID from either Vimeo or YouTube to download the highest quality video still available.

get_video_thumbnails.py

#!/usr/bin/env python

import requests
import urllib2


def download_sill_to_disk(url, target_path):
    import shutil
    req = urllib2.urlopen(url)
    with open(target_path, 'wb') as fp:
        shutil.copyfileobj(req, fp)


def get_video_still_url(video_host, id):
    vimeo_api_url = 'http://vimeo.com/api/v2/video/%(id)s.json'
    youtube_img_base_url = 'http://img.youtube.com/vi/%(id)s/'
    if video_host == 'vimeo':
        url = vimeo_api_url % {'id': id}
        r = requests.get(url)
        still_url = r.json[0]['thumbnail_large']
    else:
        base_url = youtube_img_base_url % {'id': id}
        maxresdefault_url = "%s%s" % (base_url, 'maxresdefault.jpg')
        hqdefault_url = "%s%s" % (base_url, 'hqdefault.jpg')
        still_url = "%s%s" % (base_url, 'default.jpg')

        # try and get the max resolution image
        r = requests.get(maxresdefault_url)
        if r.status_code == 200:
            still_url = maxresdefault_url

        # try and get the hq resolution image
        else:
            r = requests.get(hqdefault_url)
            if r.status_code == 200:
                still_url = hqdefault_url

    return still_url


def main():
    video_list = [
        {'video_host': 'vimeo', 'id': '12845041'},
        {'video_host': 'youtube', 'id': 'Ttp-im1F0Lk'},
        {'video_host': 'youtube', 'id': 'TOpaqDGkC_U'},
    ]
    for v in video_list:
        still_url = get_video_still_url(v['video_host'], v['id'])
        still_target_path = '/tmp/%s.jpg' % v['id']
        print "Downloading %s to %s" % (still_url, still_target_path)
        download_sill_to_disk(still_url, still_target_path)

if __name__ == '__main__':
    main()