The change in structure with size in (CO2)(N) clusters has been investigated in the crossover regime from icosahedral to cubic morphology (N=19 to 55) by molecular dynamics simulation. All the minima in the potential energy surface (PES) visited by the solid clusters at finite temperature have been characterized using a local structure analysis method. A simple picture of the change in free-energy minimum with size in CO2 solid clusters emerges from this work. It is based on the relative stability of two energy basins in the PES corresponding to the icosahedral and cubic-like structure, respectively. In addition, some evidence is provided for the existence of an icosahedral supercooled liquid in the size range near N similar to 50.