You can access the Picture/Video library since iOS 4. It does prompt at least once for location access (apparently since they can contain GPS metadata), but it does not mention anything about why it's asking for that location access.
Ah that would make sense. So that would mean that if you turn off location services any app could access your asset library without any prompt then. Good to know.
https://developer.apple.com/library/ios/#documentation/Asset...