Sadly, I can't think of any ceiling-mounted fixture that fits the bill--batteries aren't powerful enough to run lighting at the level you would want to showcase your ceiling. The best suggestion I can make is to have a floor lamp aimed up at the ceiling. You may be able to find a gooseneck floor lamp and curve the neck up so it points to the ceiling, too.

@lights online: do you have any suggestions for lights that could be swagged over to the center of the room?

Apple Pie: Certainly! In the case of swagging a ceiling light, there are lots of options in the chandelier and pendant categories. Chain-hung options can be swagged (I know from personal experience with a dining room light).

Or look into having fixtures mounted on the beam with conduit along one side -- you could get it dark or light, depending on the beam color.

Terrific, I will look into the conduit idea, or I am wondering about just painting the beam a contrasting color????