Here is a guide to photographing artwork (2d and 3d). It’s the best one I’ve found and has been very helpful to me in photographing my own work and others. It covers beginner topics as well as advanced.
If your art involves color, shape, dimension or texture, direct sunlight is the best light source, and it is widely available on this planet. Not talking about full — or open — shade (illuminated by the overly blue sky above), not dappled light (like from a tree’s varying shadows), not overcast sky light (when the sun goes behind a cloud), but direct light beamed down 93 million miles from our local star.
Direct sunlight, however, is not always available, and other natural and unnatural light sources have their qualities, too. (See Other Light, below.) They’re just not as good nor cheap nor easy to deal with as the light from the sun.