"Preliminary sketches" refers to the initial drawings or basic drafts created by an artist or designer as a starting point for a more detailed and final artwork or design. Full definition
But some represent preliminary sketches for other works of art, some finished and some not, or were made to work out the details of an idea. (ideelart.com)
All six works on paper are compositions, not preliminary sketches, just like the seven paintings. (haberarts.com)
After using preliminary sketches and maps to plan the paintings, the designs are then arranged on the floor using hand - dye fabrics in vibrant, saturated colors. (artspace.com)