Copy and past this HTML code in your group description:
<a href="http://trailr.info/main.php"><img src="http://farm4.static.flickr.com/3115/2925371686_37d54fc8ea.jpg" /></a> <a href="http://trailr.info/main.php"><img src="http://farm4.static.flickr.com/3038/2925371678_c1f9fdf699.jpg" title="[TLR-OOI]" /></a> <img src="http://farm4.static.flickr.com/3063/2925371670_4f0759f33d.jpg" title="[/TLR-OOI]"/> <a href="http://trailr.info/main.php"><img src="http://farm4.static.flickr.com/3183/2925371692_cbd32d8a7d.jpg" /></a> <a href="http://trailr.info/main.php"><img src="http://farm4.static.flickr.com/3228/2925371684_2bd0c67690.jpg" title="[TLR-OOS]" /></a> <img src="http://farm4.static.flickr.com/3063/2925371670_4f0759f33d.jpg" title="[/TLR-OOS]"/>
Preview: