After the End!?

The overworld showcases the earth (a lovely place with water, nature, greenery), the nether becomes darker and hotter that showcases venus (an endless land of ash and acid rain), the aether showcases heaven, the end showcases space (the void). The dimension after could showcase neptune, a freezing cold place with no light. A cold dimension also fits the concept of having a darker feeling the more you venture in (overworld- nether- end- the fourth dimension). This dimension have no sunlight, but it is always night. There could be small structures and a big ice palace, which the player defeats the final boss.