As you develop your installation, and particularly in the Dialogs section, there are frequent opportunities for you to preview your work. All previews use the same code as the actuall installer, so what you see is exactly what you'll get in the final installer. Obviously, when you create your installation, you want it to look as good as possible. GP-Install supports JPEG images and any bitmaps. You can specify billboard images to display during installation of your product.
Billboards can be of different sizes, and can be different graphics format.
You can add your own extensions to GP-Install. GP-Install supports both Executable extensions, and DLL extensions. Extensions are automatically comressed into your installation, and decompressed as required. The next release will have the ability to split this across floppy disks. In addition to being a very useful utility, it also demonstrates some interesting programming techniques such as using private heaps, generating executable code at run-time, tricky assembly language usage, loading DLLs dynamically and more.