Thanks for this Scott. Been testing for you and here is my feedback.

If I want to turn off images should I hard code the setting in \invoice.php? The new override settings that work with admin\invoice.php won't be pulled through.

The latest version works in PHP 7.4 but fails in PHP 8.0

Code:
[05-Feb-2023 14:11:26 Europe/London] PHP Fatal error: Uncaught Error: Undefined constant "TABLE_HEADING_PRICE_EXCLUDING_TAX" in /invoice.php:214
Stack trace:
#0 {main}
thrown in /invoice.php on line 214

[05-Feb-2023 14:11:26 Europe/London] Request URI: /store158/invoice.php?oID=31848, IP address: 77.108.141.0
--> PHP Fatal error: Uncaught Error: Undefined constant "TABLE_HEADING_PRICE_EXCLUDING_TAX" in /invoice.php:214
Stack trace:
#0 {main}
thrown in /invoice.php on line 214.
I fixed this by adding entries to my \includes\languages\english\lang.invoice.php file but don't know if this is the best way or if the error was caused by some other issue I have.

Code:
    'TABLE_HEADING_PRICE_EXCLUDING_TAX' => 'Price (excl)',
    'TABLE_HEADING_PRICE_INCLUDING_TAX' => 'Price (incl)',
    'TABLE_HEADING_TOTAL_EXCLUDING_TAX' => 'Total (excl)',
    'TABLE_HEADING_TOTAL_INCLUDING_TAX' => 'Total (incl)',
You also have two old files in your latest update. I have ported the changes across my end but so this is just for other users.
Firstly
\includes\templates\custom\templates\tpl_account_default.php
This is using
@version $Id: Scott C Wilson 2019 Jan 14 Modified in v1.5.6b $
and the latest version is
@version $Id: lat9 2022 May 26 Modified in v1.5.8-alpha $
Secondly
\includes\templates\custom\templates\tpl_account_history_default.php
Is based on
@version $Id: Author: DrByte Sat Jan 9 13:13:41 2016 -0500 Modified in v1.5.5 $
but the latest version is
@version $Id: lat9 2022 Jul 23 Modified in v1.5.8-alpha2 $