Really a matter of texturing, either add some dirt to the wall texture at the bottom or you need a different shader with an extra texture for details or something.
I mean shadowing and bump mapping will take care of that transition, but yeah if you aren’t doing that then you’d have to either change the texture or add some decals.
He’s totally using decals of spiderwebs (or dust, w/e) on the second pic, place a plane at 45º with some kind of texture for a similar effect, anyway, that’s all up to modelling or texture, but some ambient occlusion should also take care of that (bake a lightmap, and mess with the AO settings)
If you have Pro (and don’t want to go through the trouble of baking lightmaps), there’s a Screen Space Ambient Occlusion (SSAO) image effect that can put a bit of shadow in the corners.