Images specifies the images that are drawn in tabs. If DisabledImages is defined, those images are used instead for disabled tabs; otherwise, grayed versions of the images are used.  

In the implementation of TCustomTabControl, the order of images in image list properties directly corresponds to the associated tabs in the control. In the descendant class, TPageControl, this behavior is replaced by support for individual TTabSheet objects, each with an ImageIndex property. In any case, the application programmer can define customized image displays by defining an OnGetImageIndex event handler. 

OnGetImageIndex 

Pages 

ImageIndex 

DisabledImages