These are great. I'm just thinking out loud with the following:
I could definetly up my game in the nightclub photography area and gain some experience with color gels and off-camera flash.
- The white flash looks out of place so gels would make it look more 'natural', as if you weren't using a flash.
- The white flash does really well at separating the subject from the colourful mish-mash of lights and objects that would otherwise distract my eye and 'hide' the subject.
Reckon go for gels for that 'wow you got lucky with the light/how did you do that without flash' look, and 'bare' flash for busy shots where the subject would otherwise be a little too well camouflaged.
An off-camera flash placed behind your subject (well, behind as in behind relative to the camera) would also help separate the subject from the rest of the photo, so if you wanted to get away from the bare flash look experiment with that.
The lens I used was a Tokina 12-24mm for APS-C sized sensors. The results when using long exposures, zooming and using multiple flashes are pretty interesting, especially in the range where the image circle can't cover the hole sensor of my 5D, it's almost like the light trails are coming out of the picture.
These look great - the vignetting really focuses my attention and the light trails coming out of the picture adds a sense of depth. I was wondering how you managed to prevent the light hitting what I thought was a black wall in around the DJ's booth - last thing I expected was using the 'wrong' lens :-)
Other things to experiment with are leading lines, interesting viewpoints (i.e. up high and down low), shots with something small in foreground real close to camera that 'links' in some way with whats in the background (e.g. ticket stub/flyer - whatever).