Here's a fresher (and MUCH MUCH cheaper) alternative to studs or spikes: Nuts and bolts.
With some nuts and bolts and a leather punch tool, you are good to go!
P.S. For this instructable, I spray painted the nuts and bolt gold.
Step 1: The Shoe
I guess you can 'stud' anything with the nuts and bolts, but I really needed kickass shoes, so I decided to zhuzh up my pair of brown leather shoes. This pair has a foldover flap detail, which makes it perfect for adornment. Plus there will be no concern with the screw heads being in direct contact with my feet. Doubt that's gonna be comfy.