Napoleon Generalization 1
Napoleon Generalization 2
Have a look at this sketch for another arrangement of three similar triangles on the sides for which GHI is similar to the three outer triangles Napoleon Similar Triangles Variation
Napoleon Specialization: Miquel's Theorem
John Rigby from the Math Dept, Cardiff University uses tessellations in his 1988 paper "Napoleon Revisited" in the Journal of Geometry to prove Napoleon's theorem as well as some of the above generalizations.