I don't want to distract from Birdie's bass but a few things need to be cleared up.
1. You can't copyright a headstock design, period. This about trademark, not copyright.
2. You can trademark the "trade dress" of a product if you can demonstrate that customers associate the appearance with your brand name. Obviously this won't work for one bass you built for yourself, you have to be a company engaging in interstate commerce.
3. Ernie Ball has trademarks on the trade dress of their headstocks, nothing more (no matter what they may claim). They can take action against you if they feel your design causes anyone to confuse your product with theirs, but they don't "own" the configuration any more than Fender owns the 4 inline configuration. Function can't be trademarked.
Back to your regularly scheduled programming.