DIY Halloween decor ideas :: Use a white stocking with stuffing inside and add more spiders to the bottom then around. You could also put a glow stick in a water balloon and have it look like they're surrounding a glowing egg sack.
DIY Inspiration: Scary Skull Spider from Ulla.This is an easy DIY. Take a small skull (they usually come in bags, or you can dismantle the mini skeletons from the Dollar Store) and attach legs. The legs can be pipe cleaners or wrapped wire.