The 'organized' mess in Lumia's room can be somewhat of a bother, I'll like to just go wild when I'm doing the line art, and then I remember that I have to add colour to all of those objects, and they do it a way that won't inadvertently turn those details into focal points. While also keeping in mind that everything has to be relatively similar to the other panels of junk in it so it doesn't look like hr stuff is moving around the room on it's own.
Remember, tell your characters to keep their room's tidy. A little effort in their part could prevent you from having to draw a mess. I'll have to bring it up with Lumia though I doubt that she will listen to me, I guess she is at that "You're not the boss of me" age after all.
