The study of particulate suspensions flowing through narrow channels has received much attention in the last decades, especially with advance in the field of microfluidics devices. In square channels, it is known that particles in dilute suspensions migrate to equilibrium positions at the channel faces, and also at the channel corners for a channel Reynolds number above 260. However, most studies focused on very dilute systems, excluding particle-particle interactions. In this paper, we present simulations of suspensions with solid fractions up to 3%. In these simulations, we find two new patterns: at Rech < 260, the equilibrium positions split up and particles assume a staggered position, and at Rech > 260, the fraction of particles moving to the corner equilibrium positions increases with solid fraction. We present a characterization of these two effects and speculate about possible mechanisms leading to the formation of both patterns.