Performance assessment of image processing systems is typically carried out using large volumes of data with known ground truth. Unfortunately such data can be challenging to source for many problems of interest. In particular, trials data collection for performance assessment may require the acquisition of imagery for a range of sensing, target and environmental conditions. This can be time consuming and expensive to achieve. We might also wish to assess the performance of systems which are yet to be built, or over target objects for which access is, at best, limited. These problems might be addressed through the use of synthetically-generated imagery which may be produced in volume for the sensor, environment and target configurations required. If sufficiently representative these may then be used within the performance assessment process for system characterization. A scheme for the generation of synthetic imagery has previously been published. This is deemed fit-for-purpose for algorithm and systems performance assessment of image processing for Automatic Target Detection and Recognition (ATDR) tasks in Synthetic Aperture Radar (SAR) imagery. The approach is effective up to the intermediate resolutions which are typically used for ATDR applications. The input models used for synthesis are comprised of three-dimensional triangulations representing the geometric structure of the scene content, with each triangle having a parameterized scattering response based on SAR distributional models. The modelling process is reliant on a skilled analyst to identify and encode the salient detail of the target object including: the geometry of the principal structural features, and; by encoding the surface textures within the scattering response. The synthesis process generates a collection of two-dimensional arrays of distributional parameters the same size as the image to be produced. It is straightforward to use these to generate representations of expected scattering response, or realistic - looking simulated SAR images with speckle. This paper examines the development of target models for use within the simulator, along with a selection of performance assessment results produced for a range of sensor characteristics.