The "Jidaigekki ~ Taisho" category which is still rather wide open.
AMVs can be any style or audio, only the visual setting needs to be pre-1926.
This can include cuts from series that have flashbacks to those eras (as long as you are only using the period cut scenes)
Example shows include: (but are not limited to)
Kai Do Maru
Bakamatsu Kikansetsu Irohanihoheto
Harukanaru Toki no naka de Hachiyosho
Natsu no Arashi (some cut scenes)
Kazemakase Tsukikage Ran
Taisho Yakkyuu Musume
... etc ...