Not everything needs a border - it really depends on what the concept of the piece is and whether a border helps in adding to that concept or not. I don't think this piece needs one.

Onto the actual tag... I know dark is what you were going for but for me, it's a little too dark. You could try lightening it up a bit or adding in a few more colour splashes. Good job though, it's certainly different from all the generic styles around!