Show transparent version of prefab before instantiation

I am trying to create a tile editor as a plugin to Unity's editor scene view.

I have a set of tiles, and when the user clicks on the scene view, an instance of their chosen tile prefab is instantiated in the appropriate grid position. The grid position that the user is hovering over is highlighted in blue using the Handles.DrawSolidRectangleWithOutline function:

Instead, what I want is that when the user hovers over a particular grid space, a semi-transparent version of their currently selected tile brush appears over that grid space. This would act as a preview of what the scene would look like if the user were to place a tile there.

Is this possible through a custom editor script? I assume I will have to add something to my Tile Editor's OnSceneGUI function, but I am unsure what.