It may be that your email server doesn't like Zencart.
Sometimes, for the sake of everybody's time, I give up complex analysis and start fresh by repackaging the entire product.
No customization is provided for individual design elements in a product package.
You need a graphics program which will recognize psd, png, and jpg file formats, preserve background transparency, and which has "layers" capabilities. For years, I hand coded everything using Web Page Creator. Once you know enough to troubleshoot html, it is very convenient to use a good WYSIWYG editor like Front Page or Dream Weaver.
Please do verify whether you have the graphics products needed to read and manipulate the files in each products.
There is a readme file linked/attached to every product description (right underneath the product promo paragraph) which lists the file format for each file in the product.
I'll be back in a flash and let you know when I've done it.
It's always useful to keep a backup of your orders, but with the magic of pixie dust and the help of my Zencart and your name and/or email address and maybe even the order information (that wouldn't hurt) I can reset the downloads.