Wow is that your venue? It's gorgeous!! I am having an outdoor wedding in a garden, and I'm don't plan on decorating anything except the aisle and maybe some kissing balls for color. Other than that, the area is so beautiful I wouldn't want to take away from that.
The pic you have looks great! You keep it simple. Maybe some pretty lanterns down the aisle with candles (but be careful of a blowing veil with that). Maybe a rose petal path to walk down. Many outdoor ceremonies don't need much decor because the venue itself is beautiful.
The great thing about a lovely outdoor venue such as yours is really you don't have to decorate a whole lot since it's naturally beautiful in itself. But a few touches here and there will dress it up for the wedding. I saw one bride on here with a cute way to mark the aisle, on either side of the aisle (by the chairs) there were sunflowers on the ground, just the head of the flower, with no stem. You could get a similar look with daisies also.
I'm having an outdoor ceremony as well and I was thinking just some kind of flowers around the gazebo and maybe ivory sheer valance. Michelle S. that pic is BEAUTIFUL. I wonder if the flowers are meshed to the runner?