The ability to add a custom user-provided image as a loading prompt is an attractive option I would eventually like to see; under the circumstance that it doesn't completely replace or do away with the option to keep the standard WiiFlow logo animation the program is already compiled with.
As odd as it may sound, I find the WiiFlow loading animation to be rather therapeutic and relaxing as opposed to most loading screens. But I do see the benefit in having the option to customize. I would definitely use it on a future media center-focused setup.
Edit: Perhaps this feature could be incorporated as a user-adjusted line defined in something such as the wiiflow_lite.ini for people wanting to experiment with the option.
Example: [GENERAL]
"custom_boot_image=yes" would find the image in a user-specified file
"custom_boot_dir=sd:/apps/wiiflow_lite/imgs"
"custom_boot_image=no" would bypass the search for a custom image and use the standard animation provided inside the program.
In this way, the user could basically choose between "custom, but slower" and "default, but faster".
Edit2: Now that I think about it; it seems like it would probably be slower with either option introduced since the SD or USB has to first be mounted to read the wiiflow_lite.ini anyways?