This project has been in the making for months. It took some time to sort out the platform design and secure the rarer minifigs, but I'm very pleased with the end product. It's now hanging on my living room wall, where I expect it's found a permanent home.
A huge thanks to Christoph (legofenris) for generously lending me the minifigures I needed to complete the project. Don't worry, Chris—I'll be sending those back as soon as I can source replacements!
ADDENDUM: A number of folks have asked about purchasing Space Invaders. I'd be honored to build a replica for anyone interested; for pricing, please contact me directly.