Command entry: (Material Editor): Compact (Background)

Command entry:Compact Material Editor menu bar Options menu Background

Command entry:(Slate Material Editor: Right-click a material node and choose Show Background In Preview.)

Turning on Background adds a multicolored checkered background to the active sample slot. The pattern background is helpful when you want to see effects of opacity and transparency.

Left: Background on

Right: Background off

The Material Editor Options dialog also lets you assign a bitmap to use as a custom background.