For April Fool's this year, Mojang have released official Minecraft screensavers for you to use, called Minecraft Plus!.
Available on plus.minecraft.net, Minecraft Plus! is a screensaver application which can be used in the browser or can be downloaded and used as a proper Windows (7+) screensaver on your computer.
There are many different screensavers available, including one with the new glow squids swimming across the screen, and one with a camera moving over a grid of all textures in-game.
To install the Minecraft Plus! screensaver onto your computer, simply download the ZIP file and extract it in folder C:/Windows/System32. Then go to Windows Settings, click 'Personalisation', go to 'Lock screen', and open 'Screen saver settings'. Select Minecraft Plus! and apply your changes.
Minecraft Plus! is based off of the old Microsoft Plus! product for Windows XP, which includes screensavers and themes. This is reflected in the similar box art used on the Minecraft Plus! website.
If you're wanting a real update to the game this week, goats were added to Java Edition and axolotls were added to Bedrock Edition a day ago.