Here's the actual texture that we're using to generate the sky in our game. It's 1024x1024, but the actual size doesn't matter and can be any shape, according to Kyle. Feel free to start with a square texture like this one and that should provide a good starting point for the new sky textures. As mentioned before, by all means use the same colors and style that you have already been using for the dragon and the title screen for the sky as well because they look great.
P.S. Kyle was able to figure out the texture unwrapping issue with Sol. Turns out the texture loader needed to load the texture in upside down for it to display properly. In any case, the dragon loads its texture fine now and looks great.