Besides having only 26 images, among nearly 5 million, you should add more keywords to your images. I noticed for example that in the pictures of the child, you don't have the word, "kid". Or in the pictures of the dogs and the horses, you don't have the words "animal" or "animals." People won't find the pictures if they don't come up in searches. I think if you have 2 sales in only 1 month with only 26 images and so few keywords, then you'll definitely see an increase with more keywords and more images.
And of course, be patient.