Just sneaking this design in before the challenge stage closes, as I did with the official competition run by BVB themselves.

A very basic design which incorporates the famous volt colour from the Champions League win, with the black band also nodding to that, and the other colour is a metallic gold to reference Dortmund's success as well as referencing a shiny gold vintage Dortmund shirt I saw once but now can't find anywhere.

(I'm just throwing this in here because it was my entry into the official comp - I realise the quality isn't anywhere near the other entries here, which are superb.)

(I also realise how similar in spirit my design is to ONI's but I can assure you - with the assistance of timestamps if required - that I did not copy their fine work.)