You can manage icon types by toggling following classes to teaser_icon div: "gray", "highlight", "size_big", "size_small", "size_normal", "dark_bg_color", "main_bg_color", "border_icon", "round". Also you can remove button from teaser and add a link inside any header.
You can add a border or a background to any of them by adding a with_border or with_background, dark_bg_color, main_bg_color classes to teaser element.
You can style icons for side teaser same as for regular teaser
You can style icons for horizontal teaser same as for regular teaser