This is fun, just playing art director while looking at the picture books closest to me.
Here's a list of whimsical animal skilled illustrators that aren't too well known whose books caught my eye: Elizabeth Sayles, Nadia Krilanovich, Lorena Siminovich, Margie Moore, Tina Macnaughton, Marijan Ramlijak, Cee Biscoe, Neecy Twinem, Pat Schories (Biscuit series), Kristin Kest, though she's more realistic, and then there are more well known names, like Susan Hartung (mittens), Kenneth Spengler, Ashley Wolff, John Butler, Olivier Dunrea (Gossie)...
What a neat place to be in, to have imput and be a consideration for your book art. Work well done!