I guess if the gift is for a new bass player, a course would come in handy. Something that will help her/him to progress from being a beginner to becoming pretty badass.
A subscription to a bass magazine might be interesting, too. Something like this.
Personalisation or modding is another idea, I guess. Something like the rose @PamPurrs has on one of her basses (unfortunately I can’t find the picture she posted) or like the pick guard @lee_editorial improved in this thread.
If one has a talent for works like this, I think it would make a great gift. Probably there are some companies out there as well that do it professionally and that can be employed by people (like me) who could not draw a house to save their lives.