{exp:tbk_system_prefs}{system_folder}, {db_hostname}, {my_config_variable}...{/exp:tbk_system_prefs}
Inspired/lifted from the super replacements feature in LG Add Sitename
You can use any config variable you define in config.php, as well as any of the following EE preference variables:
{enable_image_resizing}{image_resize_protocol}{image_library_path}{thumbnail_prefix}{word_separator}{use_category_name}{reserved_category_word}{auto_convert_high_ascii}{new_posts_clear_caches}{auto_assign_cat_parents}{site_404}{save_tmpl_revisions}{max_tmpl_revisions}{save_tmpl_files}{tmpl_file_basepath}{un_min_len}{pw_min_len}{allow_member_registration}{allow_member_localization}{req_mbr_activation}{new_member_notification}{mbr_notification_emails}{require_terms_of_service}{use_membership_captcha}{default_member_group}{profile_trigger}{member_theme}{enable_avatars}{allow_avatar_uploads}{avatar_url}{avatar_path}{avatar_max_width}{avatar_max_height}{avatar_max_kb}{enable_photos}{photo_url}{photo_path}{photo_max_width}{photo_max_height}{photo_max_kb}{allow_signatures}{sig_maxlength}{sig_allow_img_hotlink}{sig_allow_img_upload}{sig_img_url}{sig_img_path}{sig_img_max_width}{sig_img_max_height}{sig_img_max_kb}{prv_msg_upload_path}{prv_msg_max_attachments}{prv_msg_attach_maxsize}{prv_msg_attach_total}{prv_msg_html_format}{prv_msg_auto_links}{prv_msg_max_chars}{memberlist_order_by}{memberlist_sort_order}{memberlist_row_limit}{mailinglist_enabled}{mailinglist_notify}{mailinglist_notify_emails}{encryption_type}{site_index}{site_name}{site_url}{theme_folder_url}{webmaster_email}{webmaster_name}{weblog_nomenclature}{max_caches}{captcha_url}{captcha_path}{captcha_font}{captcha_rand}{captcha_require_members}{enable_db_caching}{enable_sql_caching}{force_query_string}{show_queries}{template_debugging}{include_seconds}{cookie_domain}{cookie_path}{user_session_type}{admin_session_type}{allow_username_change}{allow_multi_logins}{password_lockout}{password_lockout_interval}{require_ip_for_login}{require_ip_for_posting}{allow_multi_emails}{require_secure_passwords}{allow_dictionary_pw}{name_of_dictionary_file}{xss_clean_uploads}{redirect_method}{deft_lang}{xml_lang}{charset}{send_headers}{gzip_output}{log_referrers}{max_referrers}{time_format}{server_timezone}{server_offset}{daylight_savings}{default_site_timezone}{default_site_dst}{honor_entry_dst}{mail_protocol}{smtp_server}{smtp_username}{smtp_password}{email_debug}{email_charset}{email_batchmode}{email_batch_size}{mail_format}{word_wrap}{email_console_timelock}{log_email_console_msgs}{cp_theme}{email_module_captchas}{log_search_terms}{secure_forms}{deny_duplicate_data}{redirect_submitted_links}{enable_censoring}{censored_words}{censor_replacement}{banned_ips}{banned_emails}{banned_usernames}{banned_screen_names}{ban_action}{ban_message}{ban_destination}{enable_emoticons}{emoticon_path}{recount_batch_total}{remap_pm_urls}{remap_pm_dest}{new_version_check}{publish_tab_behavior}{sites_tab_behavior}{enable_throttling}{banish_masked_ips}{max_page_loads}{time_interval}{lockout_time}{banishment_type}{banishment_url}{banishment_message}{enable_search_log}{max_logged_searches}{theme_folder_path}{is_site_on}{app_version}{license_number}{debug}{install_lock}{db_hostname}{db_username}{db_password}{db_name}{db_type}{db_prefix}{db_conntype}{system_folder}{cp_url}{doc_url}{cookie_prefix}{is_system_on}{allow_extensions}{multiple_sites_enabled}{site_pages}{site_id}{site_label}{site_description}{site_short_name}