If your page is named page_2 (...main_page=page_2), the image needs to be named exactly
smartbg_page_2.jpg, not smartbg_page#2_stuff.jpg.
Done
Originally Posted by gjh42
I see how you misinterpreted the instructions, as two separate steps. I will rework the readme to make it crystal clear that there is only one naming step here.
I will rework this to say
*Note*: If you have a copy of tpl_main_page.php in your custom template folder,
as you should never modify a default copy of a file.
There's no real harm done in this case. You can copy tpl_main_page.php into your custom template folder so it won't be lost if you upgrade. The edited version won't be a problem in /template_default/ for now.