So you want to use the awesome placekitten.com service from Ruby? This is what you want to use!
require 'place_kitten'
PlaceKitten.kitten_for(800, 600) # Get a url for a 800 by 600 kitten image
Put the following in your Gemfile gem 'place_kitten' and run bundle install
From your views you can now display kittens like this: image_tag(Placekitten.kitten_for(800,600))
This is git. Fork it, hack away, tell me about it!