Uploading this open source mod from Nexus Mods because it's not on Thunderstore yet.
Developer: aedenthorn
Original mod link: https://www.nexusmods.com/valheim/mods/389
To use this mod after installing it, place as many png files as you like in *BepInEx\plugins\CustomLoadingScreens*
The mod will choose one image at random for the Loading... part, and optionally another for the screen with the tips.
You can optionally add a tips.txt file with one tip per line if you want to replace the tips with your own list. Tips can be shown on both parts of the loading screen.
You can also customize the vignette, color mask, etc. in the config file.
The mod comes with an empty tips.txt file and three png files from Wikipedia vaguely related to Vikings.
The tips in the screenshots come from https://www.kickassfacts.com/viking-facts/ I make no guarantee about the veracity of the Viking facts on that site.
A config file BepInEx/config/aedenthorn.CustomLoadingScreens.cfg is created after running the game once with this mod).
You can adjust the config values by editing this file using a text editor or in-game using the Config Manager.
To reload the config from the config file, type loadingscreens reset into the game's console (F5).
https://github.com/aedenthorn/ValheimMods/tree/master/CustomLoadingScreens