Cover them in a crap fabric and hope they look less shit than when you started...
Good, glad you're with me.
Step 1: Gather the Tools
-Glue gun (or other suitable glue)
-Fabric (I had an old torn shirt)
-Foam insert for padding (assuming the foam in your headphones has disintegrated, like mine)
-Crocodile clips for holding fabric in place
Step 2: Dismantle...
Step 3: Cover All the Parts in Fabric
Slowly glue the fabric at the edges, I found the glue cooled too fast to glue more than about 25mm at a time.
Press the fabric into the hot glue and then adjust the alignment of the fabric as necessary before gluing the next section.
When you've glued it all just cut away the excess fabric and you're done.
When covering the ear pieces I found it very useful to have the foam insert in place. Thereby creating the required bulge in the fabric.
Hot glue adherers fabric to plastic, like hot shit to a blanket. It's amazing and very useful!