grub2 - Proprietary Nvidia Driver: Broken boot screen

When I first booted Ubuntu Studio, the Logo with the spinning bars was shown correctly upon startup. Ever since I installed the proprietary Nvidia driver, the splash screen is broken and I have not yet found a way to restore it.

When I start my computer, I see the BIOS screen, then it goes black, I see a small, animated Ubuntu Studio Logo inside a grey square and the rest of the screen is black, then there briefly is a bar with random artifacts shown at the top of the screen and then the desktop starts.

I have read other questions regarding issues with the splash screen when using Nvidia's proprietary drivers, however none of these solutions worked. So far, I have tried:

Finding out the supported grub resolutions with hwinfo.

sudo apt-get install v86d hwinfo
sudo hwinfo --framebuffer

Then uncommenting and setting the highest resolution in the grub configuration file (in my case 1280x1024):

GRUB_GFXMODE=1280x1024

GRUB_GFXPAYLOAD_LINUX=keep

Adding the bit-depth (x24/x16) after the resolution did nothing and is apparently not valid.

Then I found another solution suggesting to edit the following line in the same file:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset video=uvesafb:mode_option=1280x1024-16,mtrr=3,scroll=ywrap"

And also add the code:

uvesafb mode_option=1280x1024-16 mtrr=3 scroll=ywrap

To the file /etc/initramfs-tools/modules. Unfortunately this also resulted in no change at all.

Of course, I always updated grub and initramfs after every change by executing the following after every file update:

sudo update-grub2

sudo update-initramfs -u

I am not sure what else to try now. Are there any more solutions for this problem? Or would it be possible to just install another splash screen from scratch (it does not have to be the Ubuntu Studio splash screen for me or look fancy at all, but at least not broken).

By the way, I am currently using Ubuntu Studio 15.10 with an Nvidia Quadro 5000 GPU and the proprietary 304.128 legacy driver, which I have to use because of performance problems of the newest driver with Compton. I had the newest driver installed before and the problem exsisted as well, the driver change made no difference, either. Nouveau drivers are no alternative for me, unfortunately.