shedding some light on the situation

While the gallery has a lot of natural light thanks to a large window near the glass door entrance there are still track lights that could be fitted with spot and flood lights.  Spot lights give a focused beam of light onto whatever you direct the can holding the bulb.  Flood lights give a broader beam of light and gives light across a greater amount of space.

if you want to properly light a 2D work you must use indirect lighting where you take two flood lights and use the direct light bouncing off an intermediate surface onto the artwork.  The ceiling which should be white or off white  is that it produces even indirect light that doesn't fade anything in the room.  The light source should be about ten feet from the object using fifty to sixty to watt bulbs anything stronger will damage and discolor the image over time.