The GOG Spring-Sale 2020 is still in full effect.
On this occasion GOG offers the "Spring Sale Goodies Collection #1" for free until 25.03.2020. It contains artbooks, avatars, wallpapers aso.:
If you love to immerse yourself in games fully, now is the perfect opportunity. Our Spring Sale Goodies Collection #1 includes free content for some of the top titles available on GOG.COM.