I was under the impression that you wanted something like this.
If so, change references as and where required.
The Cells in Column A need the filename without path and file extension.
Sub Maybe_Try_So()
Dim PicturePath As String
Dim CommentBox As Comment
Dim i As Long
Dim fn
For i = 1 To Cells(Rows.Count, 1).End(xlUp).Row '<---- Change the 1 to the first cell in Column A with a file name without extension
fn = Dir("C:\Folder Name 1\Folder Name 2\Folder Name 3\" & Range("A" & i).Value & ".*") '<---- Change to actual Folder(s)
If Len(Dir("C:\Folder Name 1\Folder Name 2\Folder Name 3\" & Range("A" & i).Value & ".*", vbDirectory)) <> 0 Then '<---- Change to actual Folder(s)
PicturePath = fn
Application.Range("A" & i).ClearComments
Set CommentBox = Application.Range("A" & i).AddComment
CommentBox.Text Text:=""
CommentBox.Shape.Fill.UserPicture (PicturePath)
CommentBox.Shape.Height = 20 '<---- Set size or use the AutoSize
CommentBox.Shape.Width = 20 '<---- Set size or use the AutoSize
'CommentBox.Shape.TextFrame.AutoSize = True
CommentBox.Visible = False
Else
End If
Next i
End Sub