I have a graphic that is a signature that I like to put in a letter as a merge field so that when the letter is printed the signature graphic is always where it should be in the format of the letter. Is this possible? I have a global field that is a container with the graphic pasted into it.

While the graphic shows correctly as a regular field it doesn't as a merge field.

You can't use containers as merge fields. You have to put the actual field on the layout. You can place the container field directly below the letter text and have everything set to slide, so that the signature will always appear the same distance below the body of the letter.