By default, the Name / Value property is initialized by evaluating the control's PicturesName property, whose value keyword is replaced by the Index of the current layer. The Name / Value property are equivalents, so use any of them do the same. 

The control supports almost all type of pictures like

• PNG (Portable Network Graphics) is a raster graphics file format that supports lossless data compression. PNG was created as an improved, non-patented replacement for Graphics Interchange Format (GIF), and is the most used lossless image compression format on the Internet
• BMP file format, also known as bitmap image file or device independent bitmap (DIB) file format or simply a bitmap, is a raster graphics image file format used to store bitmap digital images, independently of the display device (such as a graphics adapter)
• JPEG file format (seen most often with the .jpg extension) is a commonly used method of lossy compression for digital images, particularly for those images produced by digital photography.
• GIF ( Graphics Interchange Format ) is a bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability.
• TIFF (Tagged Image File Format) is a computer file format for storing raster graphics images, popular among graphic artists, the publishing industry, and both amateur and professional photographers in general.

If using the PNG format, the control handles automatically its transparency / alpha blending, unless the Opaque property is True.  For any other picture type, you can use any of the following to define the transparent region of the picture:

• TransparentColorFrom, specifies the transparent color to define transparency part of the current picture (to). 
• TransparentColorTo, specifies the transparent color to define transparency part of the current picture (to).

The picture is displayed on the layer's background if both of the following:

• Visible property is True
• Name / Value property points to a valid picture

are accomplished.

The following properties can be used to load / import ( manually or automatically ) pictures to the layer's background:

• PicturesPath property, specifies the path to load pictures from.
• PicturesName property, specifies the expression that defines the name of the file from the PicturesPath folder to be loaded.
• Picture.Name / Picture.Value property of the Background.Picture object, defines the name of the file to be loaded ( relative, absolute, encoded or Picture object )

The PicturesPath /  PicturesName properties can be used to automatically loads files from a specified folder to be displayed on the layer's background.  

For instance, 

PicturesPath = "C:\Program Files\Exontrol\ExGauge\Sample\Design\Circular\Knob", defines default folder to load pictures from.
PicturesName = "`Layer` + str(value + 1) + `.png`", defines the name of the picture file to be loaded by the layer with the index / value. It defines the names as: Layer1.png for the layer with the index 0, Layer2.png for the layer with the index 1, Layer3.png for the layer with the index 2, and so on.

The Picture.Name / Picture.Value property of the Picture object loads a picture / graphics to be displayed on the layer's background. 

The following properties can be used to move / resize the picture on the layer's background:

• DisplayAs, retrieves or sets a value that indicates the way how the graphic is displayed on the layer's background.
• Left, specifies the expression relative to the view/current picture, to determine the x-position to show the current picture on the background.
• Top, specifies the expression relative to the view/current picture, to determine the y-position to show the current picture on the background.
• Width, specifies the expression relative to the view/current picture, to determine the width to show the current picture on the background.
• Height, specifies the expression relative to the view/current picture, to determine the height to show the current picture on the background.