1) These oil lamps @ CB2 are reasonably priced and versatile. I use mine with citronella so they burn during an outdoor gathering and keep flying critters away!
2) The outdoor cushions from Ballard come in a great selection of patterns and colors. Priced well, delivered fast, a great value.
3) Glass and copper are great materials for decorative garden items. I found these terrariums to use to cover candles, desserts, table-top displays, plants and more. Available @ A Touch of Tradition.
4) Using plants as decor is a fabulous idea. You can swap them out seasonally and this wall planter adds another dimension from standard pots on the ground. At Pottery Barn.
5) For outdoor entertaining, I love the glow and warmth of real candles. These candlesticks, from Restoration Hardware, have a great old-world feel, and are sturdy enough to place outdoors.