I only have a shelf, about a foot wide, to add decorative things (all the walls are covered in 'functional' things) and I periodically change what I have displayed there. Right now I have the darning foot, a card of snaps (for 10 cents!) a needle, different shades of thread to darn hose, an old sewing basket, and an ad from an old mag for elastic.
When my Dad and I used to go to farm auctions, I collected from the 'household' items.