It sounds like you want the image pages created, just not the tabs for them on each website page. There is no option like the option to include the Repository page in the creation options.
The tabs for the various page tabs are defined in…
gramps\plugins\webreport\basepage.py
in the program files.
Starting at line 1520 (5.1.5)
navs = [
(self.report.index_fname, self._("Html|Home"),
self.report.use_home),
(self.report.intro_fname, self._("Introduction"),
self.report.use_intro),
(self.report.extrapage, self.extrapagename, (self.extrapage != "")),
('individuals', self._("Individuals"), True),
(self.report.surname_fname, self._("Surnames"), True),
('families', self._("Families"), self.report.inc_families),
('events', self._("Events"), self.report.inc_events),
('places', self._("Places"), self.report.inc_places),
('sources', self._("Sources"), self.report.inc_sources),
('repositories', self._("Repositories"), inc_repos),
('media', self._("Media"), _create_media_link),
('thumbnails', self._("Thumbnails"), self.create_media),
('download', self._("Download"), self.report.inc_download),
("addressbook", self._("Address Book"),
self.report.inc_addressbook),
('contact', self._("Contact"), self.report.use_contact),
('statistics', self._("Statistics"), self.report.inc_stats),
(self.target_cal_uri, self._("Web Calendar"), self.usecal)
]
You could try commenting out the Media and Thumbnail lines by add a hashtag (#) to the start of these lines.
The pages should be created just not give a person easy access to them.