After having spent a few years as a craftsman in a peacetime army, there was a standardisation that tends to keep everything the same, but during times of war there were many soldiers, sailers, airmen and so on that had the support of many a good mechanic or weapons fitter that could have added almost anything to almost any vehicle in the field to suit a mission in the field.
How many times have you watched a war movie or TV show where the sparky could come up with the wildest electric gizmo, or the mechanic had done a warm-up job on the motor? And how often in real life have you done something to your car to customise it?
Although at various times and places there were shortages of weapons or equipment, many people find a way to get more than the basic equipment that is standard issue. This ranges from weapons to extra rations, and is a very common occurrence in a front line environment. Remember that German troops were no different from any other group of soldiers in that respect, and that at the time of WW2, there was still a strong reliance on horses and other beasts of burden. And an old-time re-use everything approach just like your grandfather and grandmother did.
The German society had an upper crust and a lower one just like the British did, and the officers in charge of many establishments had "family money", or other links that helped obtain equipment through "unofficial" channels. Once the war had started in earnest, and the threat of air attack became high, I'd lay bets that quite a few early tanks were "upgraded" to suit the crew.
At the other end of the stick, there would also have been many tanks that didn't have all the bits left on them as the war progressed, and if you are missing the track cover for the left rear, or the hull machine gun, as it was being repaired, or if you have a couple of dents that haven't been straightened, it's not uncommon either.
Older uniforms might have anything from mismatched colour from jacket to pants, fading, torn sections where they were snagged on barbed wire, mud, snow, sweat marks, grass stains, wet patches,........
Personalise your model and add that little bit extra that shows a human side to what you are building.