Star Wars is such a huge theme there are literally hundreds of things you could do. Here is an article I found:
I am not sure how complicated you want to get but you could do so many different things. Have you tried Googling "Star Wars Cake" I just ran a search and found about 200 ideas.
You need to narrow it down a bit if you want us to be able to give you any concrete help...
What is your skill level?
Do you want flat, tiered, or 3D?
How many people/ or how large?
Do a 3D R2D2 cake! like this : http://www.bsideblog.com/2008/06/making-the-most-amazing-r2-d2-cake-ever/
I'm just dying to make one too! Maybe my DH will get one for father's day
I have three Star Wars cakes in my pics you can take a look at ... I love the 3D look, feel free to PM me if you want to do something along those lines ...
OMG I was just asked to do one of these too! Way too many options. I am going to go back and ask them to narrow it down to a favorite character or scene or something!