I don't think giving something such as art or writings is crossing a boundary. Unless, of course, it is harmful for you or damaging to the therapeutic relationship. However, there are few instances where I feel that would be the case.

I have not personally shared writings or artwork with my current team. However, I did while I was in treatment for several months. It was very beneficial for both myself and my treatment team when I was able to share my experiences in a different medium. I tend to best express myself in my writing, but it is difficult for me to share as I am so perfectionistic and critical of how and what I write. I wish I was more confident in my ability or felt worthy of sharing such works because I do feel it could be a helpful adjunct to traditional talk therapy.

Recently, I have considered sharing something with my T. I have a dissociative disorder and another part has drawn and written something for my therapist. It's just a juvenile drawing with some words misspelled, but I have been drawn to sharing it with her. However, I feel it wouldn't be received well and I have such tremendous shame that I have resisted sharing it as of yet. That being said, more and more of these pictures and notes have been found around my bedroom and I think I will eventually need to work up the courage to give them to her.

If it is helpful and okay with all concerned, by all means, continue doing what you're doing. Helping your therapist understand you is never a bad thing in my opinion.