The framebuffer decorations are a kernel feature which allows displaying a background picture on selected consoles.
I'm not author of this patch. I actually don't understand this patch. This code has origin in last Gentoo version for 4.19 kernel. I only rebase it to new kernel versions since that time for my personal use. Therefore patch is also tested only on i915 and amdgpu drm framebuffers.
Note: Versions from 5.17 are currently broken on amdgpu after kernel commit converting amdgpudrmfb to generic fb helpers.
Use at your own risk.