Depending on the context, a painting may need a complex description. These can be especially complicated and overwhelming since art is so subjective, and if it requires a long description then the painting may be very detailed. Like all long descriptions, break it down into logical parts and start describing.
The description of a Painting needs to reference the following elements:
The Poet Centre has a few tutorials on writing Alt-text for paintings that are very helpful.
For a complex description it is important to consider the context for which you need the description. This may include:
For examples, go to Alt-text Samples: Paintings.