Making a statement with suicide is not a new concept, such as self-immolating Buddhist monks. I am not encouraging you to ctb, but I do see value in making a statement of why you are doing it if you choose to ctb. It does not seem from the OP that, like the monks, you are considering ctb as a statement, but rather making a statement concurrently with the ctb.
As @Grandexit said, there are other alternatives, such as starting a YouTube channel. You could contact other organizations and leaders in the cause of public awareness of and fighting against the causes of psych med injuries to see if there is a role for you as an activist and change-maker.
However, if ctb is your personal choice as the resolution for the problems caused by psychiatric pharmaceutical injury, then I agree with you that it is possible to make a non-graphic statement. You could wear clothing as you suggest. You can leave next to your body printouts of research regarding such injuries and accounts of similar ctbs. You can make a well-written statement out of your suicide note, including a photo of the shirt, and send it via delayed email to medical, psychiatric and pharmaceutical organizations and lobbying groups; to lawmakers; to activist organizations; and to independent and mainstream media outlets.
As feminists and post-colonial theorists have been saying for decades, the body is political. Your body and what was done to it are political. Psychiatry and pharmaceuticals are political. Whether you decide to live or to ctb, you have the power to personally and politically engage in the fight with your body, words, and actions.