Welcome to BA 
There are quite a few different ways to approach this. Let me show you a couple tricks that you should be able to adopt for your use case.
Method 1: Using 4D Voronoi, and using Random as the W. This works if the objects are duplicates or instances of each other:
You can change the spatter amount/distribution/shape/etc with other procedurals and math.
Method 2: Using Random to switch between textures:
This method will work well if you have different image textures you’re using as masks, you can just switch the Voronoi textures out for those images.
Note the LogicalAND nodes- these don’t come with Blender, they’re a group I made. That group has this:
So you can switch each LogicalAND with those three math nodes to get the same effect
Method 3: Combining both methods
You can see that Method two has the masks all in the same place. If you don’t like this, you can incorporate Method 1:
If you want more variation in the mapping, multiply the Random by X before using it as the W:
When X = 0, there will be no variation. As X increases, mapping variation increases