What is the purpose of animal images obtained in WordScape?

There is no purpose. You just collect them an can view them later if you wish.

They do have a purpose, they give you rewards--hearts, binoculars, cocoons, bees, stars, brilliance, whatever it shows for that animal in the animal chart

There are two groups of animals. The photos in the daily puzzles are just to be collected.

The animated animals in the WILDLIFE game come from hatched eggs and give you bonus stars, binoculars or cocoons during the particular event, others give bees at any time. These animals go up to level 7, and give increasingly higher number of rewards as you level up. They also give you heart gems, with which you can open more eggs.