" - more compact and more pleasing, is that the "less is more" rule?"
I only took out one image that I thought was somewhat redundant. Besides the rule of odd numbers is probably the route I took. It is an automatic for me to pick 3 - 5- etc. when doing a design. It can work with other numbers but .... the rule! There certainly are rules but once we learn them we can break them. (Or get really lucky!)
I try to keep the viewers eye in the framework of the collage. By leading the eye with the turn of a head or a lean of an animal, brings the view back to the next image. I also watch to see that there are not any contact spots that will irritate me later. Example is the hoof on top of the persons head.
The most difficult part of pricing collages for me is some just fall together easily while others take much more time. Averaging can be difficult. Also then you are selling one image with many images. People have to understand they are not just buying one image with all the work for free!