I have updated an old invoice module to 1.3.7 and done some further clean-up (for example now the fee is shown with tax in ot).
The contrib gives customers the option to select to pay by invoice. An invoice fee can be added in order total. Language files are provided in Swedish.
If tpl_checkout_payment_default.php is used (also included) then also the text in red below is shown.
Documentation is provided with the zip.
Documentation and link to download
or if installed with Payment info and image contribution:
Please report issues here. Download.