1. He took a picture of the city.
2. He took one picture of the city.
[Does #1 mean #2?]
3. He likes taking pictures with his camera.
[Is "pictures" in generic use?]
4. He took pictures of the city.
5. He took some pictures of the city.
[Does #4 mean #5?]
1 and 2 can mean the same thing -- or 1 could be meant generally. But overall, I'd say yes, they mean the same thing.
3. Yes
4 and 5 mean the same thing, yes.