Not that I'm complaining, because I love midriffs and seeing the bellybutton.
However, I have noticed (looking through many many Nilou art), even the ones that draw her normally, they show her bellybutton.
By this I mean, both her official art and her in game model, her outfit is fastened much higher on her waist, just covering her bellybutton.
Which does make sense in ensuring the outfit stays in place while moving around so much, both in dancing and fighting.
But ah well. Again, not a complaint, just a note that all artists like seeing the bellybutton.