Trackstanding/Chain Tension

OK, next question: I tightened the chain nice and tight after a pretty pathetic incident where my chain came off. Now it's making a bit of noise sort of, but I guess that's OK?

However, it's seem that when rotate the chain/cog/chainwheel rather slowly I think I can see the chain vibrate a bit.
Is this something normal I've never noticed before or is it the sign of something wrong? I am wondering if it there is an issue with the sprocket. Not sure what that could be though.
Oh, and my chainline is pretty damn straight at the moment, so no issues there I'd imagine.

don't hold onto me, but I think it sound like your chain is a little too tight mate, you should loosen it a little (doesn't feel tight when you flick it) while maintaining a straight line.