From the VirtualBox documentation:
The image must be an uncompressed 256 color BMP file without color space information (Windows 3.0 format). The image must not be bigger than 640 x 480.
Method 1 - Editing the VirtualBox VM XML
- Make sure the VM being modified is not running
- Close the VirtualBox UI
- Open File Explorer
- Navigate to the VM directory
- Open the .vbox file in a text editor
- Search for BIOS
- Add the following line inside the BIOS node
<logo displaytime="0" fadein="true" fadeout="true" imagepath="C:\Full\Path\to\BIOS.bmp" />
- Change the imagePath to the full path to the custom .bmp file
- Save the changes to the .vbox file
- Start the VM normally to test
Method 2 - Using the VBoxManage Command
- Make sure the VM being modified is not running
- Launch command prompt as administrator and run the following commands
cd %programfiles%\Oracle\VirtualBox
VBoxManage modifyvm "CaseSensitiveVMName" --bioslogoimagepath "C:\Full\Path\to\BIOS.bmp" - Start the VM normally to test