Somewhere there is a tutorial about attaching pictures, but basically you need to upload it to photobucket or something like that and then link to it in here with the insert image button, which for me is the left most second row button right under the bold button.
You have room to do some interesting things with it, but based on my friend's green, I'd be careful about making the slopes too big. His has a bump in it which is supposed to create breaking putts, but it seems to have way more effect than a real grass green would. The ball wanders off if it goes over the bump and turns in a not natural way to my eye. It works for what he needs, but I'd make sure that any break is pretty subtle.