This ruby script downloads a random photo from flickr.com (search by "1680x1050" and "nature" tags).

wallp_api.rb

require 'flickraw'
require 'open-uri'

FlickRaw.api_key="your api key"
FlickRaw.shared_secret="your secret"

args = {
	tags: "1680x1050,nature", 
	tag_mode: "all",
	per_page: 500,
	# page: 2,
}

while true	
	pictures = flickr.photos.search(args).to_a
	pic = pictures.sample
	info = flickr.photos.getInfo(photo_id: pic['id'])

	break if info.respond_to? :originalsecret
end

open(FlickRaw.url_o info) do |src|
	binary = src.read
	open("your path here/flickr.jpg", 'wb') { |f| f.write binary }
end