Here are the Dragon Ball movie posters released in Japan from 1986 to 1996 in the best quality I could find (which sometimes wasn't that great). More than one version is provided whenever available and/or when two pictures of the same poster are superior to one another in different respects (e.g. higher detail vs. less JPEG artifacts). Not sure whether there's anything left. (Note that there exist indeed additional posters with multiple Toei movies -- movies that were screened back-to-back --, but those aren't included: this is for Dragon Ball-only movie posters exclusively. Though judging by the image quality of those available online you're not missing much.)