From the ingredients you described, I would think the chicken would be slightly sweet, with a bit of saltiness from the capers and olives. That being the case, ballance the chicken with something cold and tart, like cold cottage cheese with a bit of paprika sprinkled over the top, and sitting on a leaf or two of Romain lettuce . Add to that a nice pilaf of white and wild rice, seasoned with a bit of sage or thyme, fresh ground coarse pepper, and chicken soup base. If you need another veggie, I agree that asparagus would be great, as would green beans. Or you could serve up some harvard beets for color and an added flavor. A crusty bread would be great, with real butter of coarse. I don't think you would want a toasted bread with this, so breschetta or crustini wouldn't be a great idea. Athough, using a good, fruity, extra-virgin olive oil for the bread would be something new for your guests, instead of using butter for their bread.
Don't know if these ideas fit your tastes, but I hope you can get some inspiration from them.
Seeeeeeeya; Goodweed of the North