This image shows every map projection class in d3-geo and d3-geo-projection. The total number of map projections is much larger (nearly infinite) because most projection classes represent a projection family rather than a specific projection: using projection.rotate, for example, you can specify different aspects; and many projection classes, such as conic projections, are parameterizable.
This image also does not include D3’s polyhedral projections, which are defined in d3-geo-polyhedron and are not yet updated to D3 4.0. For Dymaxion fans, see also Jason Davies’ implementation of Airocean World.