There has been a great interest in deploying large-scale Low-Earth Orbit (LEO) satellite constellations for wireless communications. This paper shows that LEO satellite constellations developed for communication purposes can be exploited for ground target imaging applications, where a unique advantage is to achieve super-high imaging resolutions that are not achievable via other imaging techniques. A new imaging algorithm is developed for this novel integrated sensing and communication (ISAC) application based on delay-sensitive signal processing and irregular sensing data exploitation. Imaging performance is analyzed. Simulations with the practical SpaceX Starlink satellite orbital data are conducted to verify both the new algorithm and the analysis results. This paper demonstrates that while the resolution of conventional satellite imaging is limited to sub-meters, the new method can potentially use only a small set of LEO satellites to achieve sub-centimeter resolution.