I almost wonder if this is in the uncanny valley between pixels and vectors. While the resolution is relatively small, I don't know if it would scream " pixel" if on a shirt, but rather just look a bit jagged. Are you wanting the pixel nature of the piece to shine through on the design? If so you might actually need to go to a smaller resolution, if not, vectors might be better.
As for the design as a whole, I think it looks cool and would make for a nice print