(I wasn't sure if this was the right forum to post such a topic, but anyway...)
I recently found my dusty Bryce 5.5 CD, and shortly found out that Blockland's default skies were actually presets within the software. I proceeded to make a bunch of skyboxes that afternoon.
Here's a sample of my work:


(Crytec is just my 483th alias in Blockland. Also, shameless patriotism.)

Now this is starting to give me vertigo.
So, if you're making a new map and need a skybox, send me a PM. Feel free to be as creative and/or ridiculous as you want. Bryce is very flexible.