You said that you want to focus on low poly stuff, so being aware of the polycount and staying in budget is a good thing to keep an eye on, but don't let it rule you. Reducing polies for optimisation is a common task during game development so it is good to know how to do it and getting used to doing it is useful. Its also good to think of LODs as you've already pointed out.
I wouldn't worry too much about those kind of aspects for now if you're just learning. Try to keep it fun - it is supposed to be fun
- and make something that looks good in the end not 'this would have looked a lot better, but I ran out of polies!'
As for the work itself, I agree with PixelGoat, the texturing style is coming along nicely. One thing to be wary of is the overuse of black. The grain in the crate would look a lot nicer (in my opinion) if it was a darker wood colour rather than pure black. Also, where you have added highlights along the edges of the dark grain could be pulled back a bit so its not so uniform.
I would also suggest painting your textures on a bg colour that is closer to your texture's main colour. If the reason for the black bg is that you are working on a UV sheet, try setting that layer to screen, moving it above your general painting layers, fade off the opacity and turn it on and off when you need to refer to it.
With your MAX render and your worry that it is washed out, don't trust that unless that is going to be your final destination for your scene. If you were to export that into UDK or Marmoset or Cryengine, it would look different. While you are working, just use the viewport as your guide rather than being tempted to alter your model to suit some lights in a render scene.
Good stuff - keep going