I couldn't find a picture of the original quilt on line but it's a good size, roughly 54 inches before the black border was added. Strange choice that was. As it was a kit it's possible there was no more fabric.
This quilt is similar in construct to one I made a few years ago where layers were fused over layers. This creates an issue of stiffness. That prevents a lot of quilting on the actual animals. Unless you can cutout the back excess the quilt loses it's ability to drape and the thick fabric eats the thread. A few good washes may help.
The story assembled on the front side of the quilt discourages a lot of standard quilting. As a result I went with marine motifs, shells, fish, turtles seagulls etc. to fill the open surfaces with quilting up to 5 inch spacing. This is the tolerance of the batting in order to keep it from moving and bunching.
I did pick out the linear boxes which added a more traditional feel.
As the pictures on the quilt are well defined I used a neutral thread, in this case a medium blue so very little of the quilted motifs are readily visible accept where they land on the black border.
This adds the feeling feel of an I SPY quilt. Lots to explore and discover.