Background images are vertically misaligned

[NoiSek]

Expected behavior When using the same wallpaper in both the theme and on the desktop, logging out of one and transitioning to the other should show both images in the same position / ratio.

Actual behavior Ratio is maintained, but the theme's background image doesn't match the vertical position of the desktop wallpaper.

Steps To Reproduce

1. Use the same wallpaper in both Aether and on your local desktop
2. Observe vertical position
3. Login to the desktop
4. Observe vertical position

Additional context See: #47