I'll look into that, then. I know that the shell namespace control panel does check the registry for entries (could you try using a program like the ReactOS Explorer to browse the control panel and see if it shows up there?), but I'm not sure if the standalone control.exe does. Ideally, the standalone control.exe would be replaced with a stub that launches the Explorer, but of course Wine doesn't have a built-in Explorer yet.
Wine's builtin control does just launch the shell's version of the control panel, unless it's given an argument like "DESKTOP", "DATE/TIME", etc. See programs/control.c.
Those string arguments to control aren't functional, because the control panel applets they reference don't exist in Wine. Launching control panel items via name is described in MSDN: http://msdn.microsoft.com/en-us/library/bb776838.aspx See especially "Executing Control Panel Items", http://msdn.microsoft.com/en-us/library/bb776841(VS.85).aspx
You might try to make some of those that have an analogue work in Wine, especially the "Legacy Control Panel Commands" "desktop" and "color". --Juan