How to do an 'Image Change' (with other info along the way)
1. Go to Waru Waru Trailer Center on the left
2. Click the middle button, something about Artists
3. This is your 'Artist List'. Your avatar will be at the top, any other online players you've recruited will also be listed here, and any extra voices you've purchased (like Barbara or Lapis) will be at the bottom. You want to click on yourself, though.
4. This screen is where you set your top 10 favourite songs. People you play with can see this list (you can see their list if you click on them on the previous screen) and it will take you to the store to buy the song you selected. You must get some kind of referral reward if someone buys a song as a result of your list--I think that's what that row of Zeroes is supposed to represent on the previous image's top screen. Anyway, to change your character, you click the icon on the bottom right.
5. You'll go through the reset process--you have to do the whole photo, voice, signature thing every time. Once done, you'll be presented with your new nickname and your appearance and given a choice.
Basically asking to confirm the 'Image Change'. I did not accept what it gave me here.
Left/Green is 'No', Right/Red is 'Yes' (just like the rest of the game, I guess). If you click no it will revert to your previous image and you can go through the process again.