Galaxy clusters are important astrophysical laboratories to study the nature of Dark Matter, whose physical properties are still unknown. Over the last decade, strong gravitational lensing has become the most powerful technique to study the total mass distribution in the inner regions of galaxy clusters, from their central brightest galaxies down to about a third of their virial radii. This remarkable progress in cluster lens modelling has been mainly possible thanks to dedicated, extensive imaging and spectroscopic surveys, carried out in the cores of a sizable sample of massive galaxy clusters. In particular, by combining the multiband imaging capabilities of the Hubble Space Telescope (HST) with the Very Large Telescope VIMOS and MUSE spectroscopic data, we have moved from lens models counting just a few tens of multiple images with photometric redshifts to a new generation of high-precision strong lensing models exploiting several hundreds of spectroscopically confirmed multiple images and cluster member galaxies. An even larger growth (from hundreds to possibly thousands of multiple images) is expected in the near future, with the upcoming James Webb Space Telescope (JWST) and Extremely Large Telescope. In this context, I will present a new, state-of-the-art strong lensing model of the galaxy cluster MACS J0416.1-2403, counting 235 spectroscopically confirmed multiple images, which form the largest secure sample ever obtained. The comparison with other models of the same cluster demonstrates that ours is better suited to accurately reproducing the positions, shapes and fluxes of the observed multiply-imaged sources..Thus, other than to robustly characterise the total mass distribution of the cluster, our model can provide accurate and precise magnification maps that are crucial to studying the intrinsic physical properties of faint, high-redshift (z > 6) sources magnified by the lens cluster.These sources, the progenitors of the galaxies in the local Universe, may play an important role in the re-ionization of the Universe, making them some of the most promising targets for the JWST telescope. During my presentation, I will present a new online tool, soon to be publicly available, that through a simple graphical interface will allow astronomers (even lensing non-experts) to take full advantage of the predictive and statistical results of these high-precision SLmodels for their research, both on the cluster lenses and on the high-redshift sources. The methodology we have started developing in these years and its future refinements are timely, since a very large number of strong lensing systems will soon be discovered in large-area surveys, such as LSST (Large Synoptic Survey Telescope) and Euclid. In the final part of my talk, I will present a novel python code that, starting from HST observations in different bands, is able to produce simulated Euclid images of galaxy clusters in the H, J, Y, and RIZ photometric filters. These simulated images, which are realistic and accurately reproduce the complexity of observed galaxy clusters, can already be used to test the robustness of cluster strong lensing models based on Euclid data only.