Those are artifacts, which are "holes" that an unsupported, old, or faulty graphics card produce when they fail, to render the game properly. Mods have absloutly nothing to do with this whatsoever, really, you most likely have onboard or built-in graphics, and you need a new graphics card. Eventually, you could easily break your computer if you do play with EPs+SPs+Mods+Store/CC, overtime.