Decorating items for Mabon: 

Hazel, Corn, Acorns, Oak, Wheat Stalks, Cypress cones, Pine cones
Myrrh, Sage, Pine
Orange, Dark red, Yellow, Brown
Acorns, Pomegranates, Pine Cones, Baskets of fallen leaves
Breads, Corn, Cornbread, Beans, Squash, Apples, Roots (carrots,
potatoes, onions), Cider

Mabon is the time to honor the Ancient Ones and the Spirit World.
Traditional Pagan activities at this time include fermenting grapes
to make wine and the decorating of graves. Also traditional is to
wander wild places and forests, gathering seed pods and dried plants.
Some of these can be used to decorate the home or altar.

Make a Indian Corn bundle to hang on your front door
Make a rattle from an empty gourd and some seeds.
Make a dried leaf mobile
How about a pine cone pyramid?
Weave some wheat into fun shapes

Tradition sees the Mabon Wreath as the primary symbol of this time of
year, the remembrance of the wheel of the year, the wheel of life,
and the promise of rebirth, both in the spring and in our next lives.

Or make a pretty fall bouquet of leaves, pine cones, corn and grapes
to leave on a grave as a gift to the ancestors.

Grapes Gourds Dried Leaves Wine Pine Cones Rattles Vines Acorns
Indian Corn Garland Wheat Sun Wheels Horns of Plenty (Cornicopia)