Status Icons have to point to real icons (.ico files, or stored inside .icl icon collections, .exe files or .dll files).
Most toolbar icon sets contain images which are the wrong size for status icons (typically 22x22 when you want 16x16) so even if we made that work, it would not be very useful.
For making "icon packs" that can be used for status icons, a .icl icon collection is recommended. Many icon editing tools can make them. (They are really just DLL files with no code and only icon resources.)