Add Driver License/Image upload in Sign

Hello All, 

I could use some help. I'd like to add a field in my document to upload a Driver License and an image upload field as well.

These EXACT examples appear in the Sign "Text Tag guide" (image 1). However, when I run a test to try different tags, I cannot get these to work at all. Other tags work fine. (Image 2 and 3)

What could I be doing wrong here? I'd appreciate if someone could guide me in the right direction. Thank you!