Maybe it's not my style so take my opinion with a pinch of salt. Hal9000 and Ono Sendai design are too basic tbh. Broseph feels much better. Also the black color really feel like it's for teenager or maybe metal vibe people (could be the customers you're targeting?). Maybe try to show different tshirt color in the front page so we know there is more than just black. Try to add more design? All the best!