i have tourrettes syndrome, and along with it i've had some really weird visualization things that are, as i was recently taught, not normal. to answer this question: depends.
sometimes i will be so zoned out that i can imagine complicated things in my head with my eye wide open and rarely blinking.
other times i can be anxious, stressed, etc, and have to close my eyes really hard in order to be able to get a general idea of what it is i want to visualize.
for quick simple things though, it is always with my eyes open. i think in pictures. when i am learning, or imagining something, it is always like a picture with a narrator, and that narrator is like if i were to be talking in real life. when i'm alone sometimes i will say what that narrator is saying out loud, but i never do in public because then i would be constantly talking. anyway cool question.
:)