Show what you have now in your phpwebgallery_image table.
How new columns would be filled?

8-)

Maybe, it would be better to create another table phpwebgallery_image_infos. I don't know right now.

id =>  mediumint(8) /* will be the same value than id in the phpwebgallery_images table */     
id_catalogo => int(11)
titolo => varchar(255)
tecnica => varchar(255)
dimensioni => varchar(255)
supporto => varchar(255)
anno => varchar(255)
mostre => varchar(255)
note => varchar(255)

How these columns would be filled?

8-)

Very nice Photon usage and an excellent sample for many people.

Back to your subject, not for tomorrow but in few days we can do it.
Because data is not coming from IPTC fields but from another db.
Yes, it would be better to create the phpwebgallery_image_infos table.

Mains lines:

1 - Picture.php will include a select on the new table and the "assign_block_vars" for them.
2 - We will modify the tpl to include the new fields
3 - Some css to show them correctly maybe.
4 - Some language change for them.

And that's it.

Be back soon.
8-)

Don't warry.
Thank you for your interest.
Bye.
lorenzo

I've tried doing the following steps, but perhaps I need a little more help  :-)

1) I've add thist line

define('IMAGE_INFOS_TABLE', $prefixeTable.'image_infos');

in ./include/constants.php

------------------------------------------------------------------------------------------
2) I've changed my image_infos coloumns name in:

id
id_catalog
title
technique
size
support
year
exhibitions
note

------------------------------------------------------------------------------------------
3) I've add this line

include(PHPWG_ROOT_PATH.'include/picture_infos.inc.php');

in ./picture.php

------------------------------------------------------------------------------------------
4) I've created  ./include/picture_infos.inc.php with

<?php

/**
* This file is included by the picture page to manage image infos
*
*/

$query = '
SELECT *
  FROM '.IMAGE_INFOS_TABLE.'
  WHERE id = '.$picture['current']['id'].'
;';

$result = pwg_query($query);
$row = mysql_fetch_assoc($result);
if (isset($row['id_catalog']))
{
  $template->assign_block_vars(
    'catalog',
    array (
        'CATALOG' => $row['id_catalog'],
        'TITLE'      => $row['title'],
        'TECHNIQUE'    => $row['technique'],
        'SIZE' => $row['size'],
        'SUPPORT'  => $row['support'],
        'YEAR'         => $row['year'],
        'EXHIBITIONS'     => $row['exhibitions'],
        'NOTE'         => $row['note'],      )
    );
}

?>

------------------------------------------------------------------------------------------
5) I've inserted these lines

<!-- BEGIN catalogo -->
<!-- for example hereunder is a table but it can be something else -->
<table class="infoTable catalog" summary="Some info about">
  <tr>
    <td class="label">{lang:Catalog}</td>
    <td class="value">{catalog.CATALOG}</td>
  </tr>
  <tr>
    <td class="label">{lang:Title}</td>
    <td class="value">{catalog.TITLE}</td>
  </tr>
  <tr>
    <td class="label">{lang:Technique}</td>
    <td class="value">{catalog.TECHNIQUE}</td>
  </tr>
  <tr>
    <td class="label">{lang:Size}</td>
    <td class="value">{catalog.SIZE}</td>
  </tr>
  <tr>
    <td class="label">{lang:Support}</td>
    <td class="value">{catalog.SUPPORT}</td>
  </tr>
  <tr>
    <td class="label">{lang:Year}</td>
    <td class="value">{catalog.YEAR}</td>
  </tr>
  <tr>
    <td class="label">{lang:Exhibitions}</td>
    <td class="value">{catalog.EXHIBITIONS}</td>
  </tr>
  <tr>
    <td class="label">{lang:Note}</td>
    <td class="value">{catalog.NOTE}</td>
  </tr>
</table>
<!-- END catalogo -->

in ./template/photon/picture.tpl

I've made a test, but I think I'm not "driving" in the right way...

1) I've moved include(PHPWG_ROOT_PATH.'include/picture_infos.inc.php');
in the first part of picture.php

define('PHPWG_ROOT_PATH','./');
include_once(PHPWG_ROOT_PATH.'include/common.inc.php');
include(PHPWG_ROOT_PATH.'include/section_init.inc.php');
include(PHPWG_ROOT_PATH.'include/picture_infos.inc.php');

----------------------------------------------------------------------------------------------
2) I've tried to put before 

//--------------------------------------------------------- picture information

this code

//--------------------------------------------------------- picture catalog
// catalog number
if (isset($catalog['current']['id_catalog'])
    and !empty($catalog['current']['id_catalog']))
{
  $template->assign_block_vars(
    'catalog',
    array(
      'CATALOG' => nl2br($catalog['current']['id_catalogo'])
      ));
}

But it doesn't seem right....

I'll try during the next weekend.
Thanks.
lorenzo