Let suppose, that you inserted wallpaper into your application. You see, that the content of left window changed and new object "VFC Wallpaper" appeared. If you select this object, then next window appears, where you can view/edit this object parameters. To edit the parameters, you must click "Edit Parameters" button ( preview regime will be locked during edit session ):

     Here you could see the basic properties of the wallpaper object:
1. Appearance. Wallpaper can appear immediately, or animated. If you select the animated scheme, then you need to set the appearance time ( in milliseconds ). Default value for appearance time - 500.
2. First application window will appear not immediately. You need to set time delay for this event ( in milliseconds ). Default value - 200.
3. Wallpaper has the background color. The default color is equal to color of your desktop window. But you can change this value. Click "Select New Color" button. You'll see the popup menu with three items - "System Color", "Custom Color" and "System Brush". If you select the "System Color" item, then next window appears:

If you select "Custom Color", then you'll select background color from the window:

If you select "System Brush", then you'll select background color from the window:

You can't select NULL_BRUSH only as wallpaper background. All other colors are available for using as background color of wallpaper object.
4. Wallpaper could consist image inside. It can be your logo, or some background. If you decide to use background image at first time ( for this application ), then you'll see the next window:

When the background image was selected, and you clicked on "Save Parameters" button, "Edit" panel will look like:

You can see that left window with program structure changed, and new object - "VFC Background Image" appeared.
5. Background image parameters. There are three variants of background image for the wallpaper. First - you use one big image only. For this case, you could use "Use image dimensions only". Second variant - you use small image, which must be tiled or stretched on some rectangular region of the wallpaper. Use, please, "Use rectangular area to display image" option for this purpose. Here you should define the width and height of rectangular area, which will be filled ( tiled or stretched ) by image. Third variant - you use image for filling all screen area. Option "Use full screen area for image drawing" helps you to do this. You must remember, that concrete scheme of image placement inside the rectangular area ( or inside all screen area ) can be defined/redefined by selecting of "VFC Background Image" item from the left window.
Also, there are two possible ways for image ( or rectangular area ) placement on wallpaper. First way - you want to align image at some corner of the wallpaper, or to center it. For this purpose, you could select "Use Predefined Type of Placement" and click on respective button below. And, the second way - you can set coordinates of left-top corner of the image on wallpaper.

In conclusion, you could also to replace current wallpaper image by new one. To do this, click on "Select New Image" button. You'll see the next window for image selection:

To accomplish edit session, click "Save Parameters Value", or "Restore Previous Parameters". If you want to save corrected GUI, don't forget, please, to visit "File" panel and select "Save Current Project As".