I don't think it would hurt to lose some of the background as long as the animals are complete. One thing you can do is take a square the size you want (a clear ruler maybe) and frame the animals in each block. Choose a size that leaves the most picture in each block. Then cut them all to that size. Then you can put a "frame" around them. How many do you have? Are you going to have to supplement them with other blocks to have enough to make your quilt?