Another 6 tees from the SegaShop online. This one has a variety of designs, some of which are a little familiar because they are variants, or, were used on other merch.
The first tee is a Forces one, with the 'good side' star logo & sihlouttes of the cast in white below it. The whole shirt is black with off-white 'stamped look' ink. Notice there's a sleeve design too, with the Forces logo, making it the most detailed of the bunch.
The next two are the same, just one in black & the other charcoal with a big bunch of characters as the only design. You can see Eggman, Rouge, Shadow, Blaze, Cream, Sonic, Tails, Knuckles, Amy & Cheese.

The following 2 shirts are also the same, but one in charcoal & the other gray. These have an all-white & line art design for Sonic, Tails, Knuckles & Eggman, but with the Japanese lettered Sonic logo in the middle. The last shirt is royal blue, with modern Sonic, Tails & Knuckles under a big modern logo with the 'swirl' light blue deisgn in the background. Each tee is a 2018 item, and about 25 dollars in adult sizes at the SegaShop

At the right there are 3 more tees. All 3 of these tees from the Sega Shop have the 2018 theme of "Colorless motion". This is where a sketchy style is used on the line art of stock art, with varying line weight & often overlapping words or other lin art for the background. It's always either white on black or black on white. Several items (bottles, tees, etc) were made with it. The first 2 tees are just opposites of each other. One black with white art, the other white with black art. And for both of them, Eggman is the star! He's drawn large & at the front of the rectangle design. Shadow is looking disapprovingly on the left side. The thrid tee is Sonic, in white (he's solid) on the black tee with the modern logo. There are words to describe him in various fonts like 'speed of sound', 'fast', 'hedgehog' & more. Each of these is about 25 dollars in adult sizes at the SegaShop online.