In this paper we present Sim-LIT, a framework for the simulation of packet loss effects on the quality of non-coded or coded still images transported over wireless sensor networks. The tool is focused on image quality assessment and it can be used to evaluate error resilience during image communications. In this first version the evaluation of block interleaving methods is provided. Sim-LIT is highly configurable, providing several options and additional tools. It may be useful to rapidly evaluate interleaving algorithms, or other techniques, or to perform extensive tests considering various image files and loss patterns. Through different simulations we demonstrate the potential of Sim-LIT as a tool for supporting research activities on the image processing and wireless sensor networks domains.