If you want a large Tux penguin sitting proudly in the dead center of your screen while Zorin OS 18 boots up—instead of the small row of penguins in the corner—you need to change the Plymouth theme rather than disabling it.
Here is how you can install a centered penguin theme:
1. Install Plymouth Themes
Zorin OS uses Plymouth to manage the boot screen. First, install the pack of alternative themes provided by the Ubuntu/Debian repositories:
bash
sudo apt update
sudo apt install plymouth-themes
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2. Restore Your GRUB Settings
If you previously changed your GRUB settings to show the top-left penguins, you need to turn the graphical splash screen back on so the center image can load.
  1. Open the file: sudo nano /etc/default/grub
  2. Change the line back to: GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
  3. Save (Ctrl+O, Enter) and exit (Ctrl+X).
3. Select a Tux/Linux Theme
One of the standard themes included in the package is called "Solar" or "Spinfinity", but if you want an exact Tux theme, you can download a community-made Knoppix-style theme from sites like GNOME-Look or Git, or use the built-in Script theme to display a custom image.
To see your currently installed themes and select one, run:
bash
sudo update-alternatives --config default.plymouth
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(You will see a list of numbers. Type the number corresponding to a theme like solar or breeze-text if you want a cleaner look, or you can install a dedicated Tux Plymouth theme).
4. Apply the Changes
Whenever you change a boot theme, you must update your system's initial ramdisk so the graphic loads before the main hard drive even mounts:
bash
sudo update-initramfs -u
sudo update-grub
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Would you like me to guide you through creating a custom Plymouth theme using a high-resolution picture of Tux so that it sits exactly in the center of your Zorin OS boot screen?

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Yes , I would like you  to guide me through creating a custom Plymouth theme using a high-resolution picture of Tux so that it sits exactly in the center of my Zorin OS boot screen?
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Here is the complete step-by-step guide to building a custom Plymouth theme that centers a high-resolution Tux penguin on your Zorin OS 18 boot screen.
We will create a theme named knoppix-tux.
Step 1: Prepare Your Tux Image
You need a high-resolution image of Tux with a transparent background (PNG format).
  1. Find or download your preferred high-resolution Tux PNG. A resolution between 400x400 pixels and 600x600 pixels works best for most displays.
  2. Rename the image exactly to tux.png.
  3. Move or copy this file into your ~/Downloads folder so we can easily copy it later using the terminal.
Step 2: Create the Theme Directory
Open your terminal (Ctrl + Alt + T) and create a new directory for your theme inside the system's Plymouth themes folder:
bash
sudo mkdir -p /usr/share/plymouth/themes/knoppix-tux
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Step 3: Write the Configuration File
Plymouth requires a .plymouth file to recognize the theme and understand which script engine to use.
  1. Create and open the file:
    bash
    sudo nano /usr/share/plymouth/themes/knoppix-tux/knoppix-tux.plymouth
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  2. Paste the following configuration exactly as shown:
    ini
    [Plymouth Theme]
Name=Knoppix Tux Center
Description=A custom boot screen featuring a centered Tux penguin.
ModuleName=script

[script]
ImageDir=/usr/share/plymouth/themes/knoppix-tux
ScriptFile=/usr/share/plymouth/themes/knoppix-tux/knoppix-tux.script
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  3. Save and exit (Ctrl + O, Enter, then Ctrl + X).
Step 4: Write the Layout Script
Now, we will write a tiny display script that calculates your exact monitor dimensions at boot time and places the image perfectly in the center.
  1. Create and open the script file:
    bash
    sudo nano /usr/share/plymouth/themes/knoppix-tux/knoppix-tux.script
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  2. Paste this exact positioning code:
    graphic
    # Load the Tux image
tux_image = Image("tux.png");
tux_sprite = Sprite(tux_image);

# Calculate the exact center of the screen
screen_width = Window.GetWidth();
screen_height = Window.GetHeight();

image_width = tux_image.GetWidth();
image_height = tux_image.GetHeight();

# Math to center the sprite
tux_x = (screen_width / 2) - (image_width / 2);
tux_y = (screen_height / 2) - (image_height / 2);

# Apply the coordinates and make it visible
tux_sprite.SetX(tux_x);
tux_sprite.SetY(tux_y);
tux_sprite.SetOpacity(1.0);
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  3. Save and exit (Ctrl + O, Enter, then Ctrl + X).
Step 5: Move Your Image Into Place
Now copy the tux.png image you prepared in Step 1 into the newly created system theme folder:
bash
sudo cp ~/Downloads/tux.png /usr/share/plymouth/themes/knoppix-tux/
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Step 6: Register and Activate the Theme
You must register your new custom creation into the system's choice menu, select it, and make sure your GRUB configurations are set up to show it.
  1. Register the theme:
    bash
    sudo update-alternatives --install /usr/share/plymouth/themes/default.plymouth default.plymouth /usr/share/plymouth/themes/knoppix-tux/knoppix-tux.plymouth 100
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  2. Select the theme:
    bash
    sudo update-alternatives --config default.plymouth
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    Look at the terminal output. Type the number corresponding to your new knoppix-tux theme and hit Enter.
  3. Verify GRUB Settings:
    Ensure the default graphical arguments are restored. Open your GRUB file:
    bash
    sudo nano /etc/default/grub
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    Make sure this line contains both quiet and splash:
    bash
    GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
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    (If you modified it to fbcon in the previous step, change it back to "quiet splash" now). Save and close.
Step 7: Build the Changes Into the System
Because Plymouth runs before your actual operating system files mount, you must bake this theme into the system's temporary boot image (initramfs).
Run these final commands to compile the theme and update the boot menu:
bash
sudo update-initramfs -u
sudo update-grub
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Step 8: Test it Without Rebooting (Optional)
Before restarting your computer, you can preview the boot screen directly in a window using this command:
bash
sudo plymouthd; sudo plymouth --show-splash; sleep 5; sudo plymouth quit
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Note: If this command opens a black window, it is usually because the plymouthd daemon is already running or your display server is blocking it. Don't worry—the ultimate test is a quick system reboot:
bash
sudo reboot
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The Result
When Zorin OS 18 boots up, your modern layout will disappear, and a beautifully centered, high-resolution Tux penguin will sit right in the middle of your display until the desktop login screen loads!