If fonts are no option, you could use images, store them in two containers in a generic settings table or similar. Anytime you'd need to display one of them, you could simply display the correct container from the settings table using a relationship between the data-table and the settings table. Also; you can make the images as plain or special as you like...
To expand on that, pop up menus and all other value lists, cannot display graphic data. If the user wants to see and and click a graphic to select that value, you'll need to put the graphic on the layout using Button Setup... to turn it into a button. Thus, you may end up with a set of 4 buttons grouped with your field where clicking one inserts data into the field.