Atmospheric muons can be used to image a volume due to multiple Coulomb scattering and absorption of different materials. This work presents the design and GEANT4 simulation of a prototype tomographer composed of two detectors, each made of two planes of an array of sensors. The sensors are based on plastic scintillators and silicon photomultipliers targeting new and costaffordable technology. In order to image a volume we study the possibility to discriminate different materials (e.g. lead, concrete, iron, water, aluminum) by measuring the absorption and incoming and outgoing angles of muons passing through these materials. We optimize the geometry and angular resolution of the array using simulations with the aim to scan structures such as large buildings and natural formations with muon tomography.