rename everything to have .bmp instead of .jpg, .png or whatever they are.

You're right - it WILL create a copy of the file because Windows must use a Bitmap image as the wallpaper. When setting a JPEG or png image as a wallpaper normally, Windows converts it internally and stores it as a Bitmap format temporarily.

What I have done to compensate for this in my wallpaper changer (Porthole: http://www.deviantart.com/view/34946883/) was to set up a check to see if there is a copy first in the original format and second in the bitmap format. If it comes back true then it deletes the bitmap copy before moving on the next image.

I'll take that as a 'no'.  

Alright, Garibaldi99 over at the WCdxforums has been great at trying to help me out. He gave me this code :

Dim fso, sourcefile
Set fso = CreateObject ("Scripting.FileSystemObject")
Set windowspath = fso.GetSpecialFolder(0)
Set sourcefile = fso.GetFile(Object.PersistStorage("picpath"))
sourcefile.Copy windowspath & "\wallpaperfile.jpg",True
system.setwallpaper windowspath & "\wallpaperfile.jpg",1


He said that it would copy the file to the windows directory before setting it as a wallpaper, and overwrite it each time.

I tested it and now it does not change the wallpaper. I'm sure it just needs a little tweaking somewhere in there but if I knew how to do that I wouldn't be here asking around.

This is my full script (with the additional code):

Sub Object_OnScriptEnter
d= weekday(date)
call Checkday
End Sub

Sub Object_OnDropFiles(files)
Dim path

path= Split(files, "|")
newpath= LBound(path)
newpath2= path(newpath)
object.PersistStorage("picpath") = newpath2
object.ToolTipText= (object.PersistStorage("picpath"))

call Checkday
End Sub

Function Checkday
d= weekday(date)
Select Case d
Case 1
Dim fso, sourcefile
Set fso = CreateObject ("Scripting.FileSystemObject")
Set windowspath = fso.GetSpecialFolder(0)
Set sourcefile = fso.GetFile(Object.PersistStorage("picpath"))
sourcefile.Copy windowspath & "\wallpaperfile.jpg",True
system.setwallpaper windowspath & "\wallpaperfile.jpg",3
End Select
End Function

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So, does anyone here have any ideas or suggestions? Here's my post at the WCdxForums:https://forums.wincustomize.com/index.aspx?ForumID=37&AID=122752#960933