I would 100000000% reupload this image with a watermark or signature baked in. It’s good original work and this is just begging to be stolen and thrown on those scammy custom tee shirt shop sites.
I think it’s a great design! I’m not sure I would love it as a tshirt, only because of the colors being a little outside my usual clothing palette. However, put it on a sticker, or a painted metal pin, or maybe a patch, or a mug…