The signs as doodles...

Aries: cute lil' flame

Taurus: A plant (Cactus/Dandelion)

Gemini: pattern of shapes

Cancer: Flowers

Leo: Stick people

Virgo: circles or spirals

Libra: rainbows

Scorpio: probably their crushes name

Sagittarius: A planet

Capricorn: Short-sayings/phrases

Aquarius: scribbles

Pisces: hearts