Look at homeworld. They have huge things that take up entire sides of the map with a gigantic scale, and no part of the skybox is the same as any other part. In Homeworld you dont see a planet in the distance, you see it up close filling your entire screen. And thus those images simply arent big or detailed enough.
Also, people seem to think that more is better, and their skyboxes end up cluttered and unrealistic. There is only 1 scene in your space scenery, possibly 2 opposite eachother, and they're hugely impacted by the lighting settings. Colour scheme and lighting is everything when making a space scene look good.
Look at homeworld 2, the tanis shipyard, with the gigantic relics in the background orbitting a blue star behind the shipyard, there are no other features of objects in that map save the shipyard itself and the ships yet it looks good.
Everything fits together in a blue atmospheric view, and the whole thing feels and looks good, and it's all lighting+skybox.
See how the whole use of lighting makes this image look good:
Everything fits and complements, including the ships.
Another aspect of skyboxes everyone gets wrong si that they plonk a planet and thats it. The entire scene is intermixed. Whats happening on part of your starscape isnt isolated and it ahs a direct consequence on the rest, else it wont look realistic, and it'll clash.
See this orange nebula goes all the way around under and over the top continuosly, surrounding the user as if it's a spherical piece of art. Now make a hole in that nebula with stars and plop one of your planet pictures in it and it'll look terribly out of place. It wont even look 3D, it'll look like a sprite...
Without the skyboxes and matching lighting, homeworld would loose about 90% of its graphical goodness, the weapons and the ships just wouldnt look right, they'd all start to clash and it'd look raw and unproffesional, as if no thought had gone into it past the models and techtree.
Your more likely to get good skyboxes out of these:
http://67.15.36.49/articles/Space/image ... e_pic1.jpg
http://67.15.36.49/articles/Space/image ... d_pic2.jpg
http://67.15.36.49/articles/Space/image ... e_pic3.jpg
http://67.15.36.49/articles/Space/image ... d_pic3.jpg
Also if you look closely at the hoemworld space scenes, they're not particularly high resolution, if anything they seem cartoony up close, yet they look brilliant because the loss of resolution is assumed to be a facet of the objects being so far away, and the fact that no one part of the skybox in a HW map is focused on by the user, rather they've been laid outto make the user want to look around than stay fixated at a spot, or they exploit lighting so that there's no need for immense detail, as the lighting on the image does all the work.
Once again I stress the importance of setting up lighting so the sun is coming from a light source that matches the light source ont he skybox and matche the hue of everything else in the skybox so that they complement. You want tod raw the ships into the scene, not the scene into the ships.. Thats why homeworld maps can seem so serene untill something comes up and a battle occurs, in which case it helps calm and concentrate you, as the music itself keys in with the whole scene. How good your space map looks is relative to the time effort and skill involved in the skyboxes creation.
