I just returned from Pittsburghs' Mexican War Historic District with some great exterior door photos. Homes were first built in this area in 1847. The architectural styles vary from Second Empire Mansards, Italianate, Richardson Romanesque, and Greek Revival. Neighboring streets also included some Victorian style homes. Thus the wide variety of exterior door styles.
Full round top door panels with applied moldings in 1 panel and 4 panel designs were popular during the Victorian era and adorned several homes adjacent to the historic district. Exterior doors with numerous small raised panels, with or without applied moldings were also abundant in many different configurations, some with glass and some without.
Many of the homes were a mixture of architectural styles. This frequently happened when the original owners preferences were not architecturally correct. After all most original owners were not architects and many probably did not hire architects to design their homes. They would put a Victorian entry on a home that may have mostly Italianate architecture simply because they liked the way it looked. They were not necessarily interested in adhering to strict architectural standards of a particular style or period.
I guess the moral to the story is, if you see an entry door you like and you like the way it looks on your house then it doesn't really matter if it is architecturally correct or not. This may offend some purists, but in the real world of architecture you can build a purebred or you can build a mutt