I did some tests with scenes to show some simple techniques for improving rendering results.
In first project i use texture for bumping. With this you`ll get very small surface details. And you can use the same texture in color channel for additional variations.
By using different noises in bump I created small surface structure and welding seam. Materials are mixed with curvative.
And sometimes you can add very simple patterns and get more interesting combinations with "the same" color base.
Of course you can use a more complex setups and blends with additional textures packs. But this is a learning project for my classes and i cann`t distribute others people textures, that`s why my goal is to show some very basic setups.