Thanks all for the replies and the links.
I've update the map: http://wlmmap.herokuapp.com/
What's new:
- go fullscreen - display wikimedia images, article and source/id - auto center when popups spans outside of the screen - uses mapbox on top of leaflet.js - uses minimap on the bottom right corner (useful?)
Behind the scene, website does not fetch data from the toolserver anymore, it uses a dedicated database that I regularily update.
I only sync'ed some of the french pictures so far to test the responsiveness of the website -- let me know how it feels.
The next step is to resurrect the form that selects with image, with article, what language, what wikipedia, etc.
By the way, any idea for a dedicated domain name?