The problem at the corners can be fixed by using the correct textures. The sides of a skybox can be mirrored but the top and bottom textures must be different. The top texture will share all 4 of its edges with all 4 of the top edge of the sides of the skybox. The bottom texture will share all 4 of its edges with all 4 of the bottom edge of the sides of the skybox.
You can't just use the same texture in a skybox IF:
The texture you are using has any type of edge continuation or edge features that are meant to be mirrored.
But if you place all the important textures in a skybox in the center of the texture then you can tile this across the entire box, but this is a severe limitation.
I've also tried making a sphere and a hemisphere around the player but it doesn't look right. There is also a method to make a small sphere 'patch' above the player - but the height must be exactly right or it does not look right at all.
Joint Ops from Novalogic uses this patch method, Freelancer uses the skysphere/skybox methods, and most of the shooters use a traditional skybox from what I can tell.
