Now, I have no idea to change it back, because I don't know where the purple background image is located, and I'm not one to mess with config files that much -- especially if you are dealing with your bootloader. I do have a source of light, though. I have heard of the Grub Customizer package, but I'm still not sure if this works with GRUB2.
I summed this up nicely in a nice sentence. This is for when I am booting into Ubuntu. It doesn't make sense, doesn't it?
Power Button >> GRUB2 with "Debian: The Universal Operating System picture" >> Kernel Boot with same image >> Ubuntu splash and so onAh well, I know one thing though. I'm never installing XFCE again from the Ubuntu repos, and I might never install it again period if I am still having a sour taste in my mouth when I do feel like installing it again on another machine.
I should mention, though, that this does not really affect my overall opinion of the desktop environment itself, because this has to do with the Xubuntu maintainers of XFCE.