ok this is what I would do to just tweak your images - I'll do them in order from the mac mini at the top and I may refer to things slightly different due to 3ds terms.
1) - its a little dark, as said, increase light output, maybe look into the fall off distance of the light, normal light reduces the further from the origin. Maybe play around with light positions, you seem to have a hot spot on the monitor foot.
- add a shadow (there doesn't look to be one), if its like 3ds max theres probably a tick box in the light properties to enable this (raytrace is best but long render times)
- add a subtle noise texture to the metal (if not there, I can kind of see it on the screen but the image is a bit small to confirm), as I've said Apples anodised metal has slight texture to it. Look at some of the close up macbook pro images to get a feel for the amount.
- Use a 50mm lens on the camera (you can set different lenses in 3ds max), closest to the 'eye' viewpoint, your perspective is a little off, I'd say you used a 35mm lens for the image.
2) - black gloss, bit too glossy in my opinion (its the same with default in 3ds max) so try to knock it down a touch, maybe reduce the amount of 'mirror' reflection given to it. The highlight also looks reddish (again same in 3ds max), try tweaking the highlight colour to a more black/white colour.
- the silver again, isn't very apple in terms of effect, once you get it though its easy enough to apply to other objects.
- flooring, the textrured mirror base could do with shadows adding (see above) as at present laptop looks to be floating, you should get a shadow of some sort on most surfaces, although obviously a mirror is less obvious.
See if theres a way to do 'reflection dimming' on the base, this would reduce the overall brightness of the floor without affecting the main image. Also consider adding a 'fall off' which would fade out the floor reflection at a given distance (this can look really nice if done well)
3) - texture is needed on the 'metal' if its metal, the colours probably aren't far off apple colours.
- lighting, maybe reposition the light(s), or if possible look for something like whats called a skylight on 3ds max (its basically a scene illumination tool as if theres a window), as the shaded ones are a tad dark. Worse case scenario add a bit of self luminance to the colours, this is usually a quick an easy trick if its not quite how you want it.
- flooring, the fall off mentioned earlier would work a treat here.
- I'd add a subtle gloss/reflection to the screen too
4) - black is too 'white' looks like it needs less reflection/gloss
- silver could do with more mirror
- I would also lower the angle of the picture but thats more of a personal thing
5/6) - just take the info from above and apply here
Just as extra things to consider as a general thing.
Depth of field (where it blurs further away) is a nice effect to know how to use, it can add a extra dimension to images and can also draw the eye to specific parts of a scene.
The 'plane' used for the base - add in an opacity layer (if you haven't got one make a square .jpg file with a radial gradient from white to black for this) so that the edges can be made transparent. So for example you can have a white floor with a black scene and the edge of the base will fade into the background rather than a harsh/hard edge.
Try to think like you're taking a photo, consider how you would light the scene if it was a real object, how would you place the camera, the lights.
Look at the materials, it's very rare to have a perfectly smooth material, theres usually a very subtle texture of some sort. Glass can have a very subtle ripple going through it, wood has the pattern etc.
Materials are the hardest, you have to take notice of them more than anything else, try to physically see/touch it.
