Consider the season; if it's fall, use a pumpkin or cornucopia filled with fake dry leaves and vegetables as a centerpiece to mark Halloween or Thanksgiving. If it's Christmas, use a miniature Christmas tree as the centerpiece with fake snowflakes scattered around to look festive. For spring and summer, use bright and colorful flowers to match the flora blooming outside.
Use rhinestones to add sparkle. You can find either self-adhesive rhinestones or you can superglue them yourself. Add these to whichever original centerpiece you choose to add extra flare.
Add matching placemats, tablecloths, and dinnerware. Having a matching color scheme helps the centerpiece really pop and everything will look put together and impressive.