A new, modular toolkit for creating simulations of 2D X-ray pixel detectors, X-CSIT (X-ray Camera SImulation Toolkit), is being developed. The toolkit uses three sequential simula- tions of detector processes including photon interactions, electron charge cloud spreading with a high charge density plasma model and common electronic components used in detector readout. In addition, because of the wide variety in pixel detector design, X-CSIT has been designed as a modular platform so that existing functions can be modified or additional functionality added easily if the specific design of a detector demands it. X-CSIT will be used to create simulations of the detectors at The European XFEL, including three bespoke 2D detectors: the Adaptive Gain Integrating Pixel Detector (AGIPD), Large Pixel Detector (LPD) and DePFET Sensor with Signal Compression (DSSC). These simulations will be available to the detector group at EuXFEL for detector characterisation and calibration. For this purpose, X-CSIT has been integrated into the European XFEL software framework, Karabo, making it available to users to aid with planning of experiments and analysis of data. In addition X-CSIT will be released standalone open source for other users, collaborations and groups to create simulations of their own detectors.