In other words a text drawing tool for the "paint" side of Decker, as opposed to a dynamic widget?

Currently the closest Decker has to what you seem to be describing is that with any widget selected, you can choose "Edit ->Copy Image" to copy an image of the current appearance of the selected widget to the clipboard. If you make a borderless, transparent field widget with the text/font/etc you want and copy the image, you can then paste it to the card background and manipulate it with drawing tools however you like.