I am currently spending my time on Photoshop, trying to work out how to lay things out. It's so massive, and such a weird shape, I'm working on a one-tenth, low res mock-up, into which I have placed scans of all the animals, so I can move things around and re-size them, until it looks OK. Then I'll re-scan everything at the right size, as the final artwork will be created digitally (in sections and at one quarter size, so my computer doesn't blow its brain).
Although my initial chase idea sounded simple, I soon discovered that, if I don't want to end up with just a 'procession' of animals, in a long, uninteresting line, I will need to draw in incidental props, like bookshelves for animals to climb onto, or chairs for them to jump over. I might need to do some graphic things will colour in the background too (like I did with the cover of Swap!), to divide up the space. Not sure yet.