my 2˘'s
It seems the largest size of the image found online is 1600 x 1200, stretching it in raster format isn't impossible, you'll need a copy that hasn't been damaged by too much jpeg compression, I've found copies of the image online that are compressed much less then others, you may get away with this... you may not...
Its a monochrome image, I found a little gaussian blur can fool the eye and soften a bit of pixel effect, under plexi and in a dim room you won't notice. I think this is a better approach then auto-vectoring. You loose a lot of nice detail doing that.
One thing you might want to try is the original artist...
http://dinyctis.deviantart.com/art/Cosmic-Frostbite-V1-860248I would try to email him and ask if you can purchase a high-res copy to use. It may be cheaper then you think and worth it in the time you'll save.
It really is a great image. (if not a bit over used for panels these days)