here's some links to materials..
I've used cloth backed vynil for covering car parts before..
As far as leather goes thinkness IMHO, should depend on how much it gets handled..
If it's too thin you may wear through it just from use..
Too thick and it will be a pita to work with..
You can do vynil on a regular sewing machine for the most part..
However for leather, depending on thinkness used will require a leather sewing maching as a standard machine may not be able to drive a needle through layers or folds on some leather types..
Sorry I don't have the pics from some vynil work I posted here a couple of years ago anymore.. :(
leather fabric | eBay
leather upholstery fabric | eBay
leather hide | eBay
carbon fiber fabric | eBay
kevlar cloth | eBay