I have a lot of sketches and tests, but I'll post them below the illustrations. Here's the final pages, without the text:
And to the sketches. First off, I had to choose which type of dog she should have.
Then I had to figure out how the girl should look.
Then I made some different coloring tests.
The first two are with watercolor and colored pencils. I liked the authentic feel, but I wouldn't know how to do an entire illustration like this, with the backgrounds and everything. Or perhaps I merely wussed out. The lack of control still gets me all sweaty and annoyed.
Here's are some with a more digital approach. They were fun to do, but I found them a little too distant and stylized for this story.
Here's another watercolor test, this time a little rougher.
Here's the first initial sketch of how the dead people and animals could look.
Here I thought I had found a balance between the digital and the analog feel.
So I tried it out on the first illustration of the book. It just didn't feel right. I went back to testing again.
In the end I figured that I needed both the flexibility of digital coloring and the authentic and feel of the hand drawn. I ended up cutting out all the characters and elements in paper, something I've never done before. Then I drew on them in pencil and scanned them with a black background so they were easily separated. And that's pretty much how I did all the final illustrations as well.
Oh, and a final thing, I did a pattern for the endpapers.