This is a perfect set for Mint Xfce, Mate and of course Cinnamon.
Try either to apply two of the best actual gtk themes... macOS and Windows 10
LightDM background you need to resize according to your screen resolution and copy to /usr/share/backgrounds
Plymouth theme you need to copy minty folder to /usr/share/plymouth/themes and apply with the standard command... which it may be different from each distro.
ADDED In case you need to change the distro icon or put a better one, this is the glossy circle used on it
AT LAST BUT NOT AT LEAST
if you having some difficulty finding your fav distro icon to apply here is the tip
go to duckduckgo and search yourdistroname logo transparent image ADDING OR NOT color
lightdm and plymouth