display picture according to a cell content

Hi all.
I have a file, attached, which displays a picture according to the content inserted into a named cell. It works nice.
I'm trying to replicate this method in another file, but I am not able to complete the process. I can't figure out how to complete the step 4, which says:
4. Next you take an arbitrary image and give it the formula '= Test'

Could someone please take a look at the file and tell me how to get to step 4?

Thanks in advance