Hi Liz,
I have to say, that I'm rather impressed with this photograph. Combining three or four photographs of race horses and then adding a sky takes quite a bit of effort, and I think you have succeeded rather well.
One criticism is that that the foreground here is blurred, as if you have applied a motion blur to it, but the horses have been frozen with a fast shutter speed. Because of this, there is a contradiction of movement.
Here is a rather simple way to adjust this.
In Photoshop open the image and then create a duplicate layer. Now, use Motion Blur to create a few pixels worth of horizontal blur on the layer.
Add a layer mask to your newly blurred image and invert it (Command+I) so that the mask changes in colour from white to black (this will hide the top layer and reveal the background layer again).
Now select the paintbrush tool, set the colour palette in the tools menu to white and paint onto the mask to reveal the forward moving legs on the horse. Remember… two of each horses legs we'll be moving forwards at almost twice the speed of the horse, while its other two legs will appear to stay still on the ground.
In the example below I have applied this technique. I have also cropped and straightened the image just a little.
Great effort. Remember, getting the bulk of the image together is usually the easy part; the devil is in the detail.
Cheers,
Anthony.
Image Doctor's edited version
