I use colours to indicate reasonable size of aircraft, and shape for navaids available. In the mean time i did also surrounding countries: like France and Italy, to facilitate people who want to fly to Iberia with interesting airports underway. First objective was to get all builtup airports in Iberia mapped for the event: The Festival of Flightgear-1&2 Nov, 2014. I overfly every airport, and if there are buildings, i land there and add it to the map.
Lately i started working on a map of airports with buildings in terrasync. These airports are marked as VOR, because there is practically only directional (and possibly DME) information available. Some airports have a localizer but no glide slope. But on mpmap you can find a VOR or NDB nearby. It can happen that an airport is a circle (no navaid). Navaids must be on the airports itself to count. You may also find a VOR on an airport when ILS is indicated. The indication is for the highest available type of navaid. I.e Airports with only lamp posts and airports with only a static aircraft planted there. I took an effort to eliminate airports with only non-building objects. The image in an airport's popup is the random object that caused the airport to be included. This map should contain all airports with buildings in terrasync. Here is a map generated out of shape files from the mapserver.