The Art skill encompasses numerous types of art. Included would
be sculpture, various types of painting, or work with many other
kinds of media. Even such diverse crafts as gem-cutting, jewelry
making, woodworking, metalworking, architecture and hairstyling
(among others) are considered to fall under the Art skill. Modern
day additions to art include photography, computer graphics, graphic
design, industrial design, animation and performance art. Art
history is more properly covered by the Knowledge skill.
Any character with the Art skill knows the fundamentals, such as the effects of different types of textures, lighting, materials, styles and perspective (if it has been discovered in their society), as well as some art history.
However, just choosing the Art skill would imply only this generalized knowledge of art, but no specific area of expertise. An art critic would typically just have the Art skill.
Instead, characters will most often specialize in a certain area. For example, a character might have skill in 'Art: Photography', which would include knowledge of the fundamentals of art, but with emphasis on photography (how to arrange subjects, select the correct film and exposure, develop negatives, and so on).
The application of this skill is very dependent on the particular situation, and is left up to the discretion of the GM. To create a work of art, for example, a character would need all the proper materials, possibly including models and a large amount of time, or a negative modifier would be applied. The more the roll is passed by, the better the objet d'art would be. (Michaelangelo had a few well-known critical successes.)