When I wrote DualWallpaper, I assumed that most users would use a third party wallpaper changing program, but have not really looked at how it would integrate with wallpaper changing programs.
I see several ways forward:
1) Implement the wallpaper changing functionality into DualWallpaper or a new program. This would mean yet another icon in the notification area.
2) Add a button to DualWallpaper to save the image to a given directory (which can be remembered between runs) and save the image using a unique filename to this directory.
3) This is something that needs more investigation, but if running on Windows 7, then see if the image can be added to the current theme.
4) Leave things as they are now so that the user has to manually add the wallpaper to whichever wallpaper changing program they use.
If anyone has any strong preferences for any of these or has any alternative ideas then please leave comments.
Number two (hee hee) sounds at the very least a good simple start. More could be added later, of course. Personally, I just use Windows' built-in functionality to change the wallpaper when I want. So something compatible with that would be good.
I like to have my wallpaper change regularly; daily, hourly, every 15 mins … .
So I hacked DualWallpaper to run with a command line argument specifying the image filename, and can run it as a Windows Scheduled Task. It wouldn't be hard to move such slideshow functionality into the c#, but as you say should this be a separate program?