The Sega Shop adds 6 more tees in 2018, and most of them are dedicated to just Tails, which is really nice to see. The first 2 are just variants (and very similar to prior releases) it's a black & dark blue version of the original Mania team with geometric shapes & the logo.
The third tee is a 25th Anniversary celebration tee featuring only Tails in the winged ring, with 25th logo & his name replacing the Sonic logo at the bottom. The gray tee has a 16-bit pixel Tails as his 'in flight' sprite...and the next tee is the same, just black. The final one has a simple orange/white

Tails face on the upper right chest area. (Usually stuff like this appears on the left....) It's the 'silouhette' type art where just the eyes are white/no other detail. All of these are about 16 dollars each in the Sega Shop in 2018.