It's all about Variety! Try these - I promise you'll feel the increased effort required to balance the offset and target your biceps in a new way!
Hand Position: Thumb Offset
With your palms facing forward, touch the outside heads of the dumbbells with your thumbs.
The benefit: As you curl the weight, you're forcing your biceps brachii (largest bicep muscle) to work harder to keep your forearm rotated outward (so your palms are up).
Hand Position: Pinky Offset
With your palms facing forward, touch the inside heads of the dumbbells with your pinky fingers.
The benefit: This tweak shifts the way the weight is distributed, providing more variety to keep your muscles growing.