Editando las propiedades del bbcode

[CORE]

javascript:

function resize(curImage, image_resize_width){
if(!curImage){
var curImage = window.event.srcElement;
}
width = curImage.width;
height = curImage.height;
if( width > image_resize_width ){

curImage.width = image_resize_width;
curImage.height = Math.ceil( image_resize_width * ( height / width ) );
}
}

function check_images(image_resize_width){
count = document.images.length;
i = 0;

while(count>i){
url = document.images[i].src;

if(!url.match(/(web-log)/) && !url.match(/(erolog)/)){
if(document.images[i].complete)
{
resize(document.images[i], image_resize_width);
}
else
{
document.images[i].onload = resize;
}
}

i++;
}
}


var image_resize_width=350;

dentro del body

onload="check_images(image_resize_width);"

y con javascript ya quedo solo tienes que agregar el html dentro de el tpl de tu phpbb

saludos