Add custom title and custom alternative text to Logo Image Settings
You can alter theme form using, form_system_theme_settings_alter in theme-settings.php

function test_form_system_theme_settings_alter(&amp;$form, &amp;$form_state, $form_id = NULL)  {

$form['logo']['settings']['alt_text'] = array(
    '#type' =&gt; 'textfield',
    '#title' =&gt; t('Alt Text'),
    '#description' =&gt; t("Alt text")
  );
$form['logo']['settings']['title_text'] = array(
    '#type' =&gt; 'textfield',
    '#title' =&gt; t('Title Text'),
    '#description' =&gt; t("Title")
  );

}


You can get this value theme_get_setting('title_text') in page.tpl.php,and i haven't tried this. Check from your side, let me know if you face any issue.