Custom Menu Background
This mod makes it easy to replace the main menu background image with one of your choosing.
While there are other mods that also replace the main menu background, they generally aim to replace it with something specific. In contrast to that, this mod is a blank slate that simply contains a placeholder background and information on how to replace it with any background you want.
After installing this mod, replace the following .DDS image file in your Steam folder:
workshop/content/400750/3305895491/resource/interface/pages/main/video_bkg.dds
The replacement should be a .DDS file – an online search for "DDS converter" provides many web-based tools as well as standalone applications to easily convert JPG/PNG images to DDS. For best results, use an image with an aspect ratio that matches your in-game resolution.
The image in the above screenshot and mod icon is also included as an example, found in the same folder as the placeholder image.