The shape of a micelle is directly dependent on the packing parameter of the surfactant.  Surfactants with a packing parameter of  ≤ 1/3 appear to have a cone-like shape which will pack together to form spherical micelles when in an aqueous environment (top in figure). Surfactants with a packing parameter of 1/3  ≤ 1/2 appear to have a wedge-like shape and will aggregate together in an aqueous environment to form cylindrical micelles (bottom in figure).  Surfactants with a packing parameter of  > 1/2 appear to have a cylindrical shape and pack together to form a bilayer in an aqueous environment (middle in figure).