@pjz99 Oh no it doesn't!</pantomimemode off>

At the moment when the system constructs the gallery thumbnail page it selects ALL the thumbnails and if the client prefs are set to "no nudity" replaces the offending thumbnails with a system generated one if the user hasn't uploaded a custom thumbnail.
What I suggested was that the page be constructed using a db query that doesn't display thumbnails for nudity/violence tagged images at all (if the client prefs are set to no nudty/violence).