For some reason, when I render out the image, it is plain white. I've checked the sky settings, and I tried applying textures, but nothing seems to change.
How can I fix this?

For some reason, when I render out the image, it is plain white. I've checked the sky settings, and I tried applying textures, but nothing seems to change.
How can I fix this?

In the 'Image Editor' window, where the white render appears, you have selected to view the alpha channel of the image. Because the image has no transparency is displays as solid white. You need to switch back to 'Color' mode to view the colours of the image: