The Custom Look module is part of the Adroit Custom bundle.
This module provides a range of options for customizing the background, font and skins used by your custom interface.
Your choices are organized into three different themes called Light, Dark and Other.
You can switch between themes by clicking on the Light, Dark and Other buttons in Custom Look. You also have the option of adding a special Theme push button to a Custom Panel module that cycles between the themes when clicked.

You might choose the Light theme to have a bright background, white knobs and black text labels; the Dark theme to have a dark background, black knobs and vivid green text labels and the Other theme to be something rather quirky.
In Custom Panel elements such as knobs have a Skin setting in their right-click menu. This enables you to choose a specific appearance for a particular element but by default they use the Theme default. In this case the skin used in each theme is set in Custom look.
Custom Look allows you to load an image to use as the background for your interface.

Each Custom Panel module has a Horizontal index setting and a Vertical Index setting that selects which part of this image to display. This means there is just one image file involved and you don’t have to chop it up into lots of sub-images – a task that could be very tedious if making repeated broad-stroke changes to your background.
The same image is shared between themes but the BRIGHTNESS setting can be different in each theme. So for instance when using the Dark theme the brightness might be turned down so much that the image is almost black.
When your patch is saved the individual Custom Panel modules chop out the bit of the image they are assigned by their Horizontal index and Vertical index settings in order to save space. The REFRESH button reverses this optimization so that you can change the index settings. You also use the REFRESH button to update the image if it is changed using a graphics editor.
Rather than use an image for the background you can use a background generated by a built-in three-color gradient shading system. This means you don’t have to worry about creating a custom image for your background while you are developing a new interface. Indeed it works sufficiently well that you may opt to simply not bother with a custom image background.

The H stands for Hue, S for Saturation and B for Brightness. The Y control moves the shading pattern vertically and the SLOPE control allows you to add a slant. If you experiment with the RANDOM button and tweak the controls you’ll soon get the hang of it. Note that the Custom panel Horizontal index and Vertical index settings affect how each Custom Panel is shaded.