First of all, the length of the main branch of the flower should be 1.5 to 2 times that of the container inch method (that is, the high caliber). Then, because your container itself has some patterns, I suggest you choose a lighter peony flower. Such as white, or pale pink. Later, because you are easy to have a beautiful arc, you can highlight this arc as much as possible when arranging flowers, don't cover it with flowers, and you can use iron wire to realize the arc in the treatment of flower branches. C or z shape is better. A fully open peony is the main branch, and then a budding peony is selected as the guest branch. Vertical or inclined can be used.

there are no particularly suitable pictures, but this can be used as a reference.