I've had this on my desktop the past couple of weeks (it's one of those wallpaper images you set to tile): "CELEBRATE!"
I had this one for a few days. Quite nice, even though it's not very accurate. The size of the moon relative to the skyline aside, having stars shine through the unseen part of the moon is rather poor astronomy. But, I still like it.
If you haven't seen the episode yet, you're going to love it, and when you do, you'll get the full effect of the joke. I laughed hard this episode.
I haven't, I must admit. I'm probably a couple behind right now which I why I usually don't plunge headfirst into episode discussions in the Brony Thread - I'm always playing catchup. I'm guessing this is some Fear and Loathing in Las Vegas takeoff and sequence, because that would be just hilarious and epic on multiple levels.