Not sure what you mean by a wallpaper stack but there are a load of free online css pattern generators where you can simply grab the code and paste it into the likes of a Sections Pro background child stack from BWD.
Apologies. I didn’t realise you were talking about a particular stack. I don’t have it so can’t comment on whether you can add your own custom pattern within it.
I believe in the second video around the 9:20 mark, he talks about custom patterns. That should help.
Just realized the websites he mentions there do not allow you to upload your image and create an SVG pattern out of that. Hopefully @joeworkman can help you out.
Rob is correct. You would need to use the Custom CSS portion of the stack. You would need to create your logo as an SVG file. Its easiest to warehouse the SVG. Then you will need to create your background css.
background-image: url('warehouse-url.svg');
Paste that background image CSS above into the stack. I didn’t add official support for this because there are somethings that would not work. You are on your own with coloring and styling the SVG. The stack settings will not work when using custom CSS. Another reason that I have not added official support for something like this is that my support inbox would be flooded with requests for help with SVGs.