Hey @natiwata! Welcome back 🙂
I'm currently working on illustrating my first picture book and I was surprised at how many changes the AD wanted at the thumbnail stage. There were quite a few rounds - but honestly, looking back she was pretty spot-on and the book will be that much better for it. I'm at final art now and two of the spreads she wanted to see in final colour along with approving everything at the linework stage. Thankfully, I had to change a lot less and I recognize that it's largely in part due to "nailing it" at the thumbnail stage. I'm hoping that when I submit all the final art there's minimal changes too because at least she liked/approved the line art and compositions already.
As much I was surprised by the rounds of changes to the thumbnails, I went to a talk with Ashley Spires recently. She's a Canadian illustrator and has done 10+ books with Canadian illustrators and is just now working on her first one with an American publisher. She said it was like night and day - that the Canadian publishers gave her so much more freedom and the American one was soooo uptight at the character design phase. She showed us her sketches she did for her character design - she gave them more than 150 options before they chose one! Yikes.
At the end of the day though, I think it depends on the publishing company and the personality of the art director whether they'll be more hands-on or not.
