After finishing the Death Star Afghan, I worked on a few other things before finally tackling this. One of my friends is a *huge* fan of both Star Wars and Mass Effect, so I combined the fandoms just for her.
The afghan is 17 squares wide and 28 squares long and about 50" x 75" after joining and the border. Each granny square is two rows big (the Death Star's were three) and they were about 2.5" wide. I used the continuous join method to throw it all together. I was smart this time and worked in all of the ends from the color changes as I was going rather than leaving it all for the end. The border is just two rows all the way around of the granny square stitch, which made the blanket edge a bit wavy.
To make the design, I first decided how many squares wide I wanted the blanket to be. Then I overlaid a grid on top of the design on photoshop the appropriate size and started filling in squares until I got the look I wanted. I've found that more complex designs require more squares, which is a lot more work and makes the afghan quite a bit bigger.
I unfortunately didn't take any in-progress pictures as I was both focusing on getting it done and trying to keep what I was doing from the recipient. All of the secrecy and work was more than worth it to see the look on her face when she opened it up last night and finally realized what it was.
Thanks for looking!