First gather all you materials.
You'll need:
- A case for your mobile phone or any device really
- Some Leather, or any material you want
- A mustache pattern or any pattern that you want, as long as it fits on the case
- A marking tool, I used chalk
- Scissors
- A needle
- A straight pin
- Strong thread, I used lika a kind of carpet thread, thin crochet thread will work too

First, trace your pattern on the back side of you leather, I used chalk because it's shows up nicely on the leather :P

Cut out your pattern.
Doesn't that mustache looks fancy ;). It kinda reminds me of Mario xD

If you have a good glue that works you should just "paint" the back of your cut out shape and glue it on and you would be done. But my glue didn't stick to the silicone so I used a different method.

Now just punch holes about 1/8" appart just a little from the edge. You could use a needle or straight pin to do this.

Now just sew your pattern right on the case with a backstitch.

Check this video to see how to do the backstitch:
http://www.youtube.com/watch?v=FQ-uYG6w_2g

You don't have to punch holes in the silicone because they will kind of dissapear. You can just sew right through it, it's really soft and easy to sew through.

Note: Cut enough thread so you don't have to tie on new string. And when you start sewing, leave a tail, you will tie the end tail to this tail at the end to secure.

I found that if you have to get your needle up from the back to the front, it's best to first poke your needle through from the front so you can see a little mark on the inside of the case. Then you know where to put your needle in from the back, and just search for the leather hole a bit. It's very do-able :P

You can see that little white dot on the left just above that point of stitches, that's what you'll see.

When you're done sewing, just tie the two ends of string together and trim it down.
Here's what the back looks like.

And you DONE!! Put your Ipod/Phone in the case and enjoy your new Mustache!