it has a nice feeling of movement, and perhaps that's what the client wnated to preserve by stopping you here. I would have drawn in the foot, even if the photo did not show it. It looks, to me, odd that it just goes to a point.
The background choice color is a nice compliment to the red of the foal, but the way it goes AROUND the foal, instead of behind him is a abit unfinished looking. You can make the foal look like he occupies real space more by having the background be a true background. You have to put it down right up to the edge of the thing in the foreground, although you need not do it if you want to keep a purely "graphic" image and are not trying for a representation of reality. Be aaware that you must have one block of color DRY before you touch another block of wet color up to it. Always dry your piece between each stage.
Also, the red brown foal will look more alive and more full of character with a vibrant eye, with a "shine spot" onit. This must be left white as you paint, since you cannot add white later, you must be careful not to paint it out as you go.
Hope that helps. Such a large piece! I rarely work larger than 24 by 16, tops.