There are both closed and open eye visuals, though personally I have nearly always kept my eyes open during DMT trips. If your eyes are open, the setting does dramatically affect the character of your trip even if you feel like you're completely out of your body and in some alternate dimension, and I would recommend doing it in the most aesthetically pleasing conditions possible. Say, outdoors on a beautiful day, or at least looking out a window. For example one time I intentionally propped myself up on my bed before smoking so when I tripped I would be looking out of the window, and when I left my body the walls pulled away from the window and I flew out over a vast beautiful field with hippies dancing around, but they were dicks to me because I'm kind of uptight in real life.
The trip's way of telling me to loosen up, I guess.
Also, something people seem to rarely talk about that really freaked me out my first time were the physical hallucinations, namely how fucking weird your body feels. I don't know if they happen for everyone but generally when I come back into my body it feels profoundly alien, like I don't even recognize my facial features by touch or anything. Once I really scared myself because it felt like there was something wrong with my dick, and when I put a hand down there to check it out it felt like it snapped right in half - it wasn't painful, but I almost shit myself anyway. Another time while exploring my mouth with my tongue I found a dragon in there, so they can be pretty cool too. The main thing is to tell yourself that nothing is permanently wrong with your body or your memory (which goes away too). It'll all come back to you just fine.
Of course, YMMV.