Customs get far far worse than people's weird sex toys - drugs, illegal meat, smuggled animals, weapons, dangerous chemicals, you name it... they're probably pretty glad to inspect your package and find nothing of any danger or note.
Also, regarding shameful boxes, I'll tell a story I've told here before;
I ordered a load of car parts once from a big online seller and they arrived at my work boxed in a huge (recycled) Tena box, with FULL embarrassing description of the contents emblazoned all over it and the security guy on reception more than a bit amused at what was apparently a massive box of adult incontinence products (even if it DID weigh an unfeasible amount and clanked when moved) with all my colleagues coming & going past it before I could get down to collect it.
So, embarrassing yes but I realised what it was and made a joke of it, and have stored that one away for future use "Ha ha, I ordered a <pick plausible thing you might order> and they've packed it in this box, that could take some explaining in the wrong situation, ha ha!"
Or you can just choose the modern excuse of eBay/Amazon picking the wrong thing - "Ha ha, I ordered a book and they've shipped me someone's diapers, must've switched the labels or something, you couldn't make it up!"