Been trawling through this site and found some cool terrain bits to share, all free.
Download free STL file Skull Bridge • Model to 3D print ・ Cults (cults3d.com)
Download free STL file Necropolis Arch • 3D printable design ・ Cults (cults3d.com)
Download free STL file 28mm Stalagmites • 3D printer design ・ Cults (cults3d.com)
Download free STL file 28mm Fire Giant’s Forge • 3D printing model ・ Cults (cults3d.com)