text: An icon simply isn't implemented in the rendering.
  
  The first issue here mentions it:
  
  https://github.com/gravitystorm/openstreetmap-carto/search?q=arts_centre&type=Issues&utf8=%E2%9C%93
  
  I guess 12,000 uses ( http://taginfo.openstreetmap.org/tags/amenity=arts_centre ) is enough for it to be rendered, the issue is probably that no one has found the time to add it.