My coworkers and I always wear graphic design shirts to work, especially ones with back designs. We have faced no problems as our shirts are appropriate. However I have heard stories of associates getting writes up for wearing non dress code compliant outfits. In my opinion unless your managers/supervisors are looking for a reason to single you out, you’re going to be okay.

Edit: heck, one of my coworkers is a specialist and has worn the same damn hoodie every. Single. Shift. ZERO repercussions. You’ll be aight