One of the goals of nanotechnology is the development of controlled, reproducibleand industrially transposable nanostructured materials. In this context, controlling of the final architecture of such materials by tuneable parameters is one of the fundamental problems. Postgrowth processes occurring in patterns grown on a surface were studied using a multi-purpose computer code MBN Explorer introduced in the present paper. The package allows to model molecular systems of varied level of complexity, and in the present paper was used, in particular to study dynamics of silver nanofractal formation and fragmentation on graphite surface. We demonstrate that the detachment of particles from the fractal and their diffusion within the fractal and over the surface determines the shape of the islands remaining on a surface after the fractal fragmentation.