How can I exclude native assets?

Hello. I’m trying to reduce the file size of my game, and I found it always import some sky box textures.
On the Android platform this are the files I talk about.

This files are from the

Well you can’t, but you can make this to reduce the file size.
If we use a custom game engine.
we can go to the source file and resize the texture.

In any photo image editor we can resize the files.
Not what I really want to do but seems to be the best option for now.