I have never personalised my basses (couldn’t ever even bring myself to put stickers on my computer), but I admire how many people have personalised their basses. Custom pick guards are a great way to give a bass a personal touch. I also have seen many basses decorated with stickers, which looked pretty nice.
I like a lot even Danny Sapko’s famous “Nope bass” (a black 5 strings Ibanez with the word Nope written in white many times all over it). I think it looks cool. Would have looked better if the pickups didn’t have “nope” written on them too, but to each its own.
If anyone wants to personalise their basses, go for it! It is your bass and you can do whatever you want with it. The only thing that matters is that you like it.
With stickers it might be a good idea to find out beforehand whether they will last, and whether it is possible to remove them without damaging the finish.