Display last topics with first topic's post image

[axew3]

Shortcode added ... it is so tricky (and could be rewrite into several different ways)
Shortcode: display phpBB last topics grid in Wordpress with first topic's attached image

how to use: [EDITED] added hint add wp_w3all.php file, missed before, and parameter for gap space between columns

a simple/basic working example is here:
phpbb-grid-list-of-latest-topics-with-attachments