Always glad to help. The reason why vectors are your best choice: embossing and foil applications are separate processes from printing. They can be done on blank and printed paper and also combined together. The special effect is applied to the area that is defined separately. This can be any shape and text. No shades are supported, no partial transparency and no other effects, just simple, plain shapes.
You can achieve this with transparent PNG but this will trigger the converting tool within the designer. Vector graphics saved and uploaded as PDF, AI or even SVG (used only as symbols in the designer) give you always sharp, clear contours at any size, no matter how you resize, rotate or transform them.
As an example, I once created a business card for a client with some content in braille. I chose the embossed business card option (wasn't on Z) and in addition to the normal design for printing including the braille text, I added a separate PDF consisting solely of the brail dots (it depends on the printer, how you have to deliver it). The result was a card with printed braille text that was also embossed. Works the same way with foil.
