When you think about it the humble microphone does receive a lot of abuse especially in the hands of a vocalist. So often the headshell is dented, and the body is chipped and overall it looks like it has had a hard life. To improve some of the appearance would be to try and re-shape the headshell, this especially true with the Shure SM-58, or other mics with a similar headshell. With this type of microphone you can use a screwdriver handle to push out the shape. You need to be careful as there is usually some foam rubber inside the headshell. The body of the mic could be carefully repainted with a matte metal spray paint. If you are going to paint the mic you need to protect all surfaces and bits and pieces of the mic that you don’t want to get paint on. Or you could sand it down for that brushed metal look. But there is one thing we all need to think about in relation to mics, and that is the fact that they get spat on, coughed into etc. Now this does not sound pleasant and there is the slight possibility of and infection being transfer ed by mics from one performer to another. I suggest at regular intervals the headshell gets a wash and maybe once a week it gets a spray of disinfectant to kill the bugs. Something like Glen-20 would work nicely, just make sure that you don’t spray the important working of the mic.