The administration of the "articles_layout" sppagebuilder addon is broken. After wasting a couple of hours to find out what was broken and nothing was being displayed in "choose layout", here's a fix:

Edit templates/newsberg/sppagebuilder/addons/articles_layout/admin.php Add the following line after Line 16: $activeTemplatePath = Uri::root().'templates/newsberg/sppagebuilder/addons/articles_layout/assets/images/';

Now replace the following block:

'articles_layout' => array(
                    'type' => 'thumbnail',
                    'title' => Text::_('COM_SPPAGEBUILDER_ADDON_ARTICLES_LAYOUT_STYLE'),
                    'desc' => Text::_('COM_SPPAGEBUILDER_ADDON_ARTICLES_LAYOUT_STYLE_DESC'),
                    'values' => array(
                        'arabica' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/arabica.png',
                        'liberica' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/liberica.png',
                        'bourbon' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/bourbon.png',
                        'robusta' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/robusta.png',
                        'java' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/java.png',
                        'excelsa' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/excelsa.png',
                        'casipea' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/casipea.png',
                        'geisha' => str_replace('administrator/', '', Uri::base()) . 'images/demo/article_layouts/geisha.png'
                    ),
                    'std' => 'arabica',
                ),

with this block:

'articles_layout' => array(
                    'type' => 'thumbnail',
                    'title' => Text::_('COM_SPPAGEBUILDER_ADDON_ARTICLES_LAYOUT_STYLE'),
                    'desc' => Text::_('COM_SPPAGEBUILDER_ADDON_ARTICLES_LAYOUT_STYLE_DESC'),
                    'values' => array(
                        'arabica' => array(
                            'title'=>'arabica',
                            'icon'=>'<img src="'.$activeTemplatePath . 'arabica.png'.'"></img>'
                        ),  
                        'liberica' => array(
                            'title'=>'liberica',
                            'icon'=>'<img src="'.$activeTemplatePath . 'liberica.png'.'"></img>'
                        ),  
                        'bourbon' => array(
                            'title'=>'bourbon',
                            'icon'=>'<img src="'.$activeTemplatePath . 'Bourbon.png'.'"></img>'
                        ),  
                        'robusta' => array(
                            'title'=>'robusta',
                            'icon'=>'<img src="'.$activeTemplatePath . 'robusta.png'.'"></img>'
                        ),  
                        'java' => array(
                            'title'=>'java',
                            'icon'=>'<img src="'.$activeTemplatePath . 'java.png'.'"></img>'
                        ),  
                        'excelsa' => array(
                            'title'=>'excelsa',
                            'icon'=>'<img src="'.$activeTemplatePath . 'excelsa.png'.'"></img>'
                        ),
                        'casipea' => array(
                            'title'=>'casipea',
                            'icon'=>'<img src="'.$activeTemplatePath . 'casipea.png'.'"></img>'
                        ),
                        'geisha' => array(
                            'title'=>'geisha',
                            'icon'=>'<img src="'.$activeTemplatePath . 'Geisha.png'.'"></img>'
                        )   
                    ),
                    'std' => 'arabica',
                ),

For those who come after.