Buy Directly from the UE4 Marketplace:

This pack included 150 decal materials, perfect for environments. Bullet holes, large patches, cracks and more.

Features:

PBR setup- Diffuse, Normal, RMA (Roughness, Metalness, AO), Opacity Concrete, Fabric, Wood, Rebar, Brick, Vines and Metal

Texture Resolutions: 4096x4096