You need :

• Sinatra >= 0.9.1 for use of send_data method
• Ruby Mapscript

Any configurations you can change in whooms.rb

• For people who want to serve just the one image and don’t want to go through the palaver of setting up their own mapserver.
• Find a geotiff (ideally in epsg:4326 projection), upload it, and you will get a WMS link, and a permalink to that page.
• Use the WMS link in your favourite WMS viewer / openlayers / JOSM / GoogleEarth e.t.c.