What do percussion instruments actually look like?

To generalize somewhat. There are many different types of percussion instruments. A percussion is basically any musical object that you hit with a stick to make a sound.

A drum is usually a rounded piece of wood or metal with a plastic, cloth, or vinyl on top that is hit to produce a sound.

A triangle is a percussion instrument and is a piece of metal shaped like a triangle with a gap in one corner.

A xelephone has different shaped blocks that are hit to make different pitched sounds.

Cymbals are flattened pieces of metal shaped into a circle.

A piano is also considered a percussion instrument. The list goes on and on.