Hello.  I was introduced to this forum by a person from a bow forum and have enjoyed reading about slinging.  Very cool.  I just wanted to pass along something I have done for my bows that you folks might be able to do too.  If you search the internet for tribal tatoos you can find some really neat ones.  Since tribals are just black and stencil-like, you can print it out on thicker paper and cut out the black parts.  Then use this as a stencil and fill it in holding it to your leather pouch.  Use a permanent marker and spray with a coat of matte finish to seal the image.  Since you won't want to seal the whole piece of leather, you could just cut out another stencil of a circle and put that over your image so your spray will coat a circle with the pattern in the center.

Hey bob,

Great idea! I just found a neat celtic knot pattern and drew it on the back of my sling with a pen. It looks really cool.