Don't worry about them I'd say. One day you're going to know if they are ready or not, although the more experience you have, the more mistakes you are going to see in your earlier works 😀
Salvador Dali's style would be excellent. I'm not really familiar with it, so it would be a great way to learn :)
Van Gogh on the other hand is familiar, I've been to the Van Gogh museum in Amsterdam, have seen his works, at least a part of them exhibited there.