Panna cotta, at its most basic, is just milk and cream jelly. The jelly may be served as it is, but that'd be quite boring.
How to liven up plain panna cotta?
Make it heart-shaped. Make it in bright colours.
Looking good is half the battle won. Tasting good is the other half.
Raspberries work like a charm in panna cotta. They brighten the blandness of milk and cream with a tart fruitiness.