For my tile project i am thinking of doing it on the design process. Though for my metaphors i am going to base it around a common theme of pirates. The idea is to have slogans saying each stage, then having realistic sketches of almost a pirates take on it. i.e. "collect the pay" is a picture of a treasure chest. Also i had the idea of having one picture that comes together it makes a subtle picture of a treasure map, this being a metaphor of the journey to become a graphic designer.
Its not a lot but i really think that the idea will come together really well. it is up my alley theme wise and i look forward to drawing the slides.