Something that's easy to try is to add a "DoEvents" statement to the end of any loop that's doing a large number of iterations.

Example:
    'Gets image URL, finds image on server and inserts in in the active cell
    For counterRow = Cells(Rows.Count, columnImage).End(xlUp).Row To 1 Step -1
        On Error Resume Next
        strImage = Cells(counterRow, columnImage).Value
        Cells(counterRow, columnImage).Activate
        Selection = ActiveSheet.Shapes.AddPicture(strImage, False, True, ActiveCell.Left + 4, ActiveCell.Top + 4, 86, 70)
        DoEvents
    Next counterRow