Putting a patterned fabric onto a shaped chair back is a cutting problem before it is a covering problem.
Most people assume the motif is simply placed in the middle. It is not that simple, because a cartouche back is not a rectangle - it is wide at the shoulders, narrow at the waist and rounded at the base, so its visual centre is not its geometric centre. Centre a medallion by measurement and it sits low; centre it by eye against the shape and it sits where it belongs.
Then there is the padding. The back is domed, so the cloth stretches as it goes over - most at the crown, least at the edges. A motif cut to look right flat comes out slightly wider and shallower once it is on, so the cut has to anticipate that distortion and allow for it.
And the repeat has to be considered across the whole chair. If the seat carries the same fabric, the motifs on the back and the seat should relate rather than fight - which usually means cutting them from the same length, in sequence, and accepting the waste that creates.
Our upholsterers lay out the pattern on the finished frame before a single cut is made, mark the centre lines on the cloth itself, and only then start. It is the difference between a patterned chair and a chair with pattern on it.