XF 1.3 bbcode post background

[pelzo2]

hello,
been looking around for few days now on the forums , gave everything a try before i annoy you with my question , but found no way so we could reach this .
our forum is launching this sunday and this is an important and highly requested feature by users and our team members.

we found this thread that request the same thing but it wasn't answered
http://xenforo.com/community/threads/it-is-possible-to-make-background-for-posts.47874/

here is an example :

usualy the code you post in the thread to show the background is something like
[TBL] image link.png[/TBL]
so the user don't need to upload it they just need to grab a link

so here i created an example so you could understand what we want to achieve

i got 3 random backgrounds :
http://www.menuiserie-billeaumetais.fr/wp-content/uploads/Light-Wood-Background-Wallpaper.jpg
http://www.opinews.com/wp-content/uploads/2014/01/Background-Light-Blue.jpg
http://www.psdgraphics.com/file/yellow-lights-background.jpg

and i will be using them as backgrounds for our post

so the post code will be something like this :

"
[TBL]http://www.menuiserie-billeaumetais.fr/wp-content/uploads/Light-Wood-Background-Wallpaper.jpg[/TBL]


TEXT TEXT TEXT

[TBL]http://www.opinews.com/wp-content/uploads/2014/01/Background-Light-Blue.jpg[/TBL]

TEXT TEXT TEXT

[TBL]http://www.psdgraphics.com/file/yellow-lights-background.jpg[/TBL]

"

and the result will be this :

http://i.imgur.com/HuS2N9Q.jpg


if its not complicated would it be possible to provide us the steps needed so we could achieve this on xenforo because we have no idea how to start or what to do.

thank you !