New Feature
Custom Backgrounds
[user request]

Now you can have a custom background for the viewer with many options to play with.
- You can pick any image as background.
- Mix both image and solid color, by adjusting the image opacity. If the image has transparency (like .png files) - it will also be respected.
- You can make the image grayscale, to make it less distracting (and more cool).
- Choose anchor point to stick the image to any edge, corner or the center of the window.
- Choose tiling options.
- Store your custom backgrounds.
- Have separate backgrounds for Fullscreen and Window Mode, or link them to use the same settings.