Have only played one course a couple of times with no tee markers. It isn't that big a deal after one or two holes. Sometimes it is a bit annoying actually as you might be playing a tee favoring you or your opponent time after time. No use adding that to the game of golf.
My preference is for small, simple items, like a small stick, maybe even painted. Small manufactured items like discs, often found in UK, are fine as well.