Not going to judge the merit of this (I can't really say whether the advance time is useful or not). I question the need for vote disabling. It seems odd to have the posts available for viewing, but not voting.
Mechanically, we cannot prohibit voting except by locking each post. Only moderators can lock posts, however, and they have to manually do so. In order to facilitate such a mechanical solution, you'd need a moderator to be patrolling the thread constantly to ensure that s/he can lock any new answers the moment they get posted. It's not very sustainable option to have to keep on that, and it also has the negative point that locking prohibits editing and comments as well.
This is also too much of a niche utility within the sites to warrant a custom solution, I would think. There aren't all too many reasons out there to disable voting across all answers of a question, so I do not expect that this kind of suggestion would get very far in being a whole new feature.
That leaves the rather lackluster option of "trusting your users" by including some disclaimer at the top of the post to note for how long users should not vote. Users who go over to the Meta are usually very obedient to that kind of instruction so it has some potential to work.
You could consider recommending users to use our Save Draft functionality. Post the new thread early, as you recommend, and then include a disclaimer at the top suggesting users to rely on drafts when uploading their photos "early". All you need to do is enter text into the answer - after a short period of time, a draft will be auto-saved, and will persist for about a week. That way, you'll have the photo loaded early, but it cannot be viewed or voted on until the post "officially" opens, which is what I gather to be your goal.