Tente esta modificação:
Sub InstallPictures_2()
Dim i As Long, v As String, shp As Shape
For i = 1 To 1000
v = Cells(i, "A").Value
If v = "" Then Exit For
With ActiveSheet.Pictures
.Insert (v)
Set shp = ActiveSheet.Shapes(ActiveSheet.Shapes.Count)
shp.Top = Cells(i, "B").Top
shp.Left = Cells(i, "B").Left
shp.Height = 100
shp.Width = 100
End With
Next i
End Sub