Giraffe lend themselves to a vertical format so well. When I put them in a tall painting, I like to have some horizontal elements to create a soft balanced composition. If I was going for drama the horizontal components wouldn't be as important.
Below you can see the compositional elements.
I am far from an expert on this. Mostly I design by feel with little intellectual calculation. I am sure I miss some critical opportunities for a better composition on some pieces. Then again, maybe there are some of my paintings which have design elements which don't fit the "normal" conventions for composition but the paintings really work.