The filename or HTTP URL of the picture displayed over the button surface when the button is disabled.
Supported bitmap formats are BMP, ICO, GIF, JPG, TIF and PNG.
If the filename is an HTTP URL you can use the proprietary format AMZ.
If you need to download the file from an FTP URL you can use the SetPictureFromNet method.
To make the picture background transparent use the PictureTranspMode property.
To render a picture color transparent use the PictureTranspColor property.