This is rarely a BIOS issue; it is usually due to a bad game rip or incorrect rendering settings (try switching between Vulkan and OpenGL).
If you want to see the classic Sony PSP wave and logo when you boot a game, you need the original firmware files.
The only legal way to obtain these files is to dump them from your own PSP using custom firmware (CFW). Troubleshooting Common Issues
Even though it isn't strictly required for gameplay, users often look for BIOS or firmware files to enhance the "authentic" feel of the console or to fix specific issues:
The short answer is . Unlike many other emulators (like those for the PS2 or PS1), PPSSPP is designed to simulate the PSP's operating system functions internally.