To be fair, most of the ones I've seen aren't pure beheadings. They're mostly throat-cutting, shootings, and beatings.
Let's say, for the hell of it, that you're right. I have a new one. I bet if we went back and forth alternating between Islamist and Russian snuff films, but with the caveat that each video had to be from a different individual or interest group (whichever happens to be represented in the video), you'd run out way before I would.
Let's be honest, most of those Islamist beheading videos come from one or two groups. See what I'm getting at?