I made a UDF to copy Images to the Clipboard. You can use all formats of GDIPlus, but Transparency is not supported.
ImageClip.au3:
#include <ClipBoard.au3>
#include <GDIPlus.au3>
;===============================================================================
;
; Function Name: _ImageToClip
; Description:: Copies all Image Files to ClipBoard
; Parameter(s): $Path -> Path of image
; Requirement(s): GDIPlus.au3
; Return Value(s): Success: 1
; Error: 0