Leaflet is really nice. I used it to render a big map of my drawing game ScribbleGrid:

http://scribblegrid.com/maps/origin/

I used Node.js Canvas to render a file of each room, ImageMagick morgify/montage to add grid borders as well as combine them into one big image and GDAL2Tiles to split the image up into parts in a "z / x / y" folder structure for Leaflet to fetch.