It is possible to display a raster on a Discover cross section, however, it will require the registration of the image to the cross section coordinates.

Please note that Discover cross sections are only in 2D space in a non-earth meters projection. See the related articles for more details. 

The the process is the same as you would register any other image, i.e. use Discover>Images>Rectify Image.

All you will need to do is have both your unregistered image file open in MapInfo along with the Section you want to register from.
The Rectify Image tool will allow you to register control points on the image which relate to control points on the registered cross section.

When you are registering the image for the cross section do this in Non Earth (Meters) coordinate space as the cross section window is located in Non-Earth (Meters) coordinate space

Also if you save the image in the section folder, and prefix the file name with the section .e.g. "Section1_Image.tab", it will then automatically open/close with the Section Manager and other section layers.