Spotify makes it clear that username is used to identify you.
But, there is good news since Spotify does allow you to change the display name.
At the top of the display, tap your currentdisplay name.
It doesnt matter if you also touch on theView Profileoption, youll end up on the same page.
Select theEdit Profileoption thats right under your current username.
Tap on the change photo option and choose from where you want to upload the picture.