If you're making a 3d game you have to have something at "infinity". It can be a color or you can map an image onto points at infinity.

You can draw on a flat surface and then you can project it.

But what if you assembled your image from hexels (yes, hexagonal pixels). Just like in low-level pixel land you have color and up/down left/right. On the inside of a sphere you can't do that. But you could build a while "2D" graphics library from the ground up that writes in hexels onto a sphere (inside or out).