BTW, you can edit your fixed image into the original post instead of the badly downscaled one, this will probably improve your response rate as people tend to look mainly at whatever the first thing is in the thread. Just make sure to mark it as an edit (I just write EDIT: before anything like this, myself).
Shading
I am assuming in this photo that light is coming from a ceiling light in the center of the room. I just need help getting started on shading techniques. One I see an example and know the rules of shading, I can go from there. I saw some examples online but none of them show the light source in the room like this.
Arne has a nice tutorial on shading, light and color with plenty of illustrative images,
http://androidarts.com/art_tut.htmIt's pretty simple really though: The light comes from the source, hits a plane of the object and bounces, and finally reaches the camera/eye. The angle between the lightsource and the surface limits the amount of light that you can possibly perceive (== how much light is actually hitting the surface), and the angles between the surface, the camera, and the light effects whether there is a highlight visible, and if so, how much. Highlights are less necessary for basic lighting, so I won't talk about highlights any more here, except to say that the light vs surface relation is called 'diffuse' light, and the light vs surface vs camera relation is called 'specular' light.
The properties of the material itself also gets involved in how much light the camera can possibly perceive on a surface, but that's not necessary to understand for a basic grasp of shading.
If you're interested in the theoretical basis for the above, look up raytracing.
You seem to have a reasonable grasp of the above principles -- perhaps you just need to begin applying them in all situations? It's fundamental light physics, so there really aren't any situations in which it doesn't apply.
The Cord
I want a cord coming from the stereo to the wall outlet. I cannot get this to look right and still be isometric. Also I am not sure my wall plate is scaled correctly. The speakers in this room are greatly exaggerated just as they are in the game and this makes scaling items trickier.
This is really a problem of understanding how to project things in 3d space. If you only have a basic understanding of that, then it's too much to expect that you will be able to readily lay out a curve through 3d space. One neat way to manage this and improve your projection skills is tessellation. Place some waypoints, just dots where you want the cord to pass through; consider them as one of the corners of a square or cube if that helps. Make sure that those waypoints are correctly placed in 3d space. Then draw a curve that passes through each of these waypoints smoothly.
Then, if you understand where those points are in 3d space, you can shade the cord accurately. This is the key aspect to making the cord fit in 3d space -- If you project it well, but shade it badly, it will still look 'out of space'.
BTW, further on the 'tessellation' subject, there's nothing wrong with making a really angular cord that is not curved at all -- as long as it's correctly projected, then you can always turn that series of lines into a series of curves just by incrementally subdividing them.
Speakers
I really need some tips on shading the speaker cones and making the speaker dust caps look spherical.
If you understand what I wrote above about how light interacts with surfaces and the camera to produce the final perceived light level, then this is actually simple -- the light level changes smoothly as the angle changes, for both cones and spheres (the main difference being that spheres curve in three dimensions but cones only curve in one dimension -- so cones are actually very simple to shade).
If not, messing around in a 3d program like Blender, adding some basic shapes like spheres and cones and seeing how lights interact with them, is a pretty good educational tool.
My only direct critique is, because this is so big, I think you are unlikely to learn much -pixel art- technique from it, though you will certainly improve your draftsmanship. Consider whether this matches your priorities for this picture.
Oh, and you might want to increase the overall contrast so it's easier to see any shading errors. Putting it on a neutral grey (#808080 or #bababa) could also help you pick colors more accurately -- using a white backdrop often encourages oversaturated color choices.
