maybe you could also try the type of paper that comes in long rolls... sort of like Christmas paper... the back of it where.. it is white.. with no.. print.. they make white paper like that... or if you have old wrapping paper... you could put that up... and have it so that the whole wall is covered...
and... they have washable markers.. too in case... it goes thru the paper....and having red markers.. that are not permenant... (washable)... might help him.... and then eventually.. when he feels "heard"... he might try drawing with some of the other colors...
I agree with pegasus... that your little has something to say..
making him be quiet... will hurt you the "adult"..
can your T... draw him out.... and help you to set some parameters... like no hurting your body with sharp stuff... or can you reach inside.. and give him permission and understanding... telling him it's ok to draw... just not "hurt" his/your body???
One of my alters likes to shread.... and so she uses a paper shreader... you would have to make sure... it was "child proof"...
Before paper shreaders... she used to rip paper.. apart... or at resturants she would rip napkins into smaller.. and smaller.. and smaller pieces...
This is a very calming activity.... really.... my son and ex-husband.. don't understand - but they do not know I am DID...

for you... and "little"