I actually do not mind making gallery subpages but we do need to figure out how we are going to seperate things. Like for example, will the sections be listed according to Manga (Naruto, Boruto), Anime (Part I, Part II, Boruto), Movie (Naruto, Boruto), Games (Part I, Part II, Epilogue), etc.
Is it really necessary when we have the categories though? Can't we just leave a link on the respective pages somewhere? Some wikis integrate the gallery into the infobox, but the gallery can have its own section on the page.