In the Amuse app
You can change the artist profile in the app. Go to the user profile in the app and upload a photo. However, it will only be used as part of your profile on Amuse.
If you have signed up using Facebook, we will use your Facebook profile picture as the user profile in the app. Same goes for Google. But you can still change the user picture in the app. See above.
In the stores
When it comes to the artist picture in your profile in the different stores, you need to contact them directly. Check their brilliant FAQ.