CC Image Sources
This page is to track the information we learn about databases of images and their APIs. Tracking bug is here.
Wikimedia Commons
I used wimgs to download images from specific categories and it worked for that purpose. It's written in Ruby which is not nice. But it uses the Mediawiki API which is just URLs returning JSON.
Metadata
Download entire collection
Formats
Primarily JPG files (with various extensions), also PNG and GIF (including animated GIF), SVG, and even videos.
Push
Flickr Commons
Flickr API - https://www.flickr.com/services/api/ along with Python API (https://code.google.com/p/flickrpy/) provides a way to download images using different parameters.
This Python program available here - https://github.com/annafatsevych/images-flickr Will download the images (true to their posted format on Flickr - PNG, GIF(non-animated),and JPG - based on the specified date as well as the CC License selected (multiple licenses can be selected) - https://www.flickr.com/services/api/flickr.photos.licenses.getInfo.html
It uses two method calls:
photos.search(date, license) - to get all the images with the date and license parameters photos.getInfo() - to get the information about the author (Flickr's user ID, and registered user name for licensing purposes, and original URL for attributions)
Flickr API offers many methods - this is one way to use them and will be updated with further optimizations.