Because two pieces of calligraphy must be adjacent and tied together.

have

A (2,2) * A (2,2) = 2 * 2 = 4 kinds.

Paintings can't be adjacent, and then illustrate between calligraphy and design.

There are three spaces, insert two pictures, and there are a (3,2) = 6 kinds.

A total of 4*6=24 species.