Ghost Shader
This is a simple additive parallax shader with up to 3 layers. You can use any texture. If you want to aniamte a layer with the speed parameter, use a tilable image from a texture pack of your choice or an AI tool like midjourney (use "--tile").
This shader pack has some examples that you can directly use in your world or customize to your needs. it is made for VRChat but its compatible...