Hi!
Foxes are my girlfriends favorite animals and she is giddy with delight after reading your brief.
So, I'd like to help you out.
I like the style you are going for, the line with accentuated coloring in places, that could work like a charm. Akin to Saul Bass' style, but with more outlines. Or like the comic book covers of Dave Johnson (100 Bullets) but more sketchy. Rough lines in ink or pencil and added color in Photoshop, that could do it.
I am very much into picture books and PB design (and have done two myself) so I'd like to work with you on this one.
Please let me know.
Regards,
Marko