Property bags for the shell (Shellbags) support is unimplemented

Shellbags is an undocumented feature added in windows XP that allows per-folder settings to be saved. Things such as per-folder icon size, the item positions, (logical) view mode, fflags, etc are all stored in shellbags. This is also used under XP to store desktop display settings and icon positions, etc. (in a slightly different way than folders)
Some documents that relate to shellbags, can probably get some useful info:
http://www.williballenthin.com/forensics/shellbags/
https://www.sans.org/reading-room/whitepapers/forensics/windows-shellbags-forensics-in-depth-34545
related kb issue article:
http://support.microsoft.com/kb/813711

Documentation of the functions implementing this:

http://www.geoffchappell.com/studies/windows/shell/shlwapi/api/propbag/index.htm

http://www.geoffchappell.com/studies/windows/shell/shlwapi/api/util/loadfrompropertybag.htm 

http://www.geoffchappell.com/studies/windows/shell/shlwapi/api/util/iunknown/queryservicepropertybag.htm

Apparently it's also on MSDN now (Windows 7+):

https://msdn.microsoft.com/en-us/library/windows/desktop/ff728867%28v=vs.85%29.aspx

Related methods:

https://msdn.microsoft.com/en-us/library/windows/desktop/bb761919%28v=vs.85%29.aspx

Contains information pertaining to "bags":

http://newsoft-tech.blogspot.com/2008/04/case-of-thumbsdb-file.html

There is also a function in Shell32.dll named "SHCreatePropertyBag", which we have a stub of.