Finally found a way to do something 'decent' with the background...
There are always a lot of distractions in a photo of a horse show...
Other horses, other jumps, people, banners, etc...
This one was done using the clone tool and the 'barbouillage' on GIMP..
Nothing fancy, but for me, if this was my horse and me on it, I'd prefer this kind of background instead of one where I can see someone picking his nose

It is extremely hard to get good pictures of jumping horses, so thinking about bohkey (whatever the spellng is) is out of the question for me.
I only had my 50 mm lens and couldn't get closer than this to a jump.
http://farm5.static.flickr.com/4152/5007913967_1b26ac1461_z_d.jpg
Camera Canon EOS Digital Rebel XSi
Exposure 0.001 sec (1/1600)
Aperture f/2.8
Focal Length 50 mm
ISO Speed 400
Exposure Bias +2/3 EV
Exposure Program Shutter speed priority AE
You need at least a 7D to take REALLY good pictures of horses. I'd skip the 5d and go to the 1d series after that.