Learn English – Someone who looks for problems and is not interested in solving an issue pragmatically

I think you can use a night owl, or a night-person.

I think a sleepless man is fine. Another similar word is an insomniac (a person who suffers from insomnia), but I believe that you know it already.

Actually, what you describe sounds pretty much like me myself. :)

Sometimes, people called me a vampire, a batman, or a dark knight, which is not quite to my taste. In casual chatting, I personally prefer a night dweller or a man of the night more.

Here is an excerpt from Wikipedia's page Night owl:

A night owl or evening person is a person who tends to stay up until late at night. The opposite of a night owl is an early bird, a lark as opposed to owl, someone who tends to begin sleeping at a time that is considered early and also wakes early.

You mention two different use cases.

an eye for detail in arts ... an eye for detail, which is why a photo was taken from the right angle or perspective

Like jimsug and ChristopherW, my immediate inclinations are meticulous and keen- or sharp-eyed. I don't know of a single adjective (or even a concise phrase) which has this meaning and also carries a specifically artistic connotation. I can only recommend general terms and suggest that you add modifiers to specify the artistic bent. Other potential choices:

• Assiduous
• Sedulous
• Scrupulous (very often used in a moral or ethical sense)
• Fastidious (very often used when speaking about cleanliness)
• Detail-oriented

an eye for detail as to what is the cause of a conflict (something which other people hadn't seen yet)

For this case, I'd use astute. 1, 2. It applies specifically to situational assessment, and I would not use it to describe an artist's attention to detail, e.g. when painting or composing a photograph.