A call to https://en.wikipedia.org/wiki/Special:ApiSandbox#action=query&format=json&prop=pageimages&titles=San+Francisco&piprop=thumbnail%7Cname&pithumbsize=250&pilicense=any
allows us to return the thumbnail url where the width is 250

However in the MCS for use in apps they want to be able to request urls for 3 sizes - 250, 640, 480 and 1024

We can rely on find and replace - but a better long term solution would be to add support for multiple pithumbsize parameters...