An index of map icons from four sources:
Most of these icon sources use open licenses. Maki, Temaki, and the OSM lane icons all use a CC0 license. The Weather Underground Icons use an MIT license. The OSM map icons use an unspecified PD style license. The Calcite icons are available under the Esri Master License Agreement (MLA). The NPMap Symbol Library is created by the National Park Service so is assumed to be a Public Domain work in the U.S..