I’m testing providing the ability to provide bulk download files by month. You will need a program like 7-Zip (it’s free and open source) to open these compressed files. WinRAR, WinZip and others should work well too. For now, here are the wallpapers from May, June and July 2016:
Organizing the images by month and selecting the right ones to ensure there are no/minimal duplicates is time intensive and the bandwidth usage is higher so this is in the experimental phase. If this works well more months may be considered for bulk download.