Here's some things you need to think about, although
I'm not sure you will get it working with this:
Ensure the loader in C: gets run (C:AFA_OS_Loader, you cannot use "Run" to launch it) before IPrefs/VP Prefs.
Do a C:Assign AFA_OS_Libs: SYS:AFA_OS:Libs
if it complains about missing assign.
Move the picturedatatype to the disabled directory inside the AFA_OS_Libs directory (it doesn't seem to work)
Also, I haven't look at AmiKit yet, but if it's heavily patched with MCP
and other stuff, AFTER the AFA_OS_loader has been started, the
manual states that the new functions *could* be overwritten, AFAIU.
This could be the reason why you get that error message.
But anyway, keep on trying. You might get it working.