A few weeks ago a comment was made that more disco set ups would benefit from £40 being spent on them than £400.
I would say that your rig appears to be just that.
If I was really, really trying hard to find any area's for improvement on your rig, it would definately be under the heading of "On stage presentation" rather than "functional excellence". You've already got a very effective show.
You've already taken the first step in hiding cables etc by using the cloth over your table to cover a multitude of ugly wiring etc.
Other members have already mentioned using velcro strips to tidy up cables further - eg: the overhead ones etc. If possible, give the speaker cables some stress-relief using velcro at intervals down the tripods length. At the moment it looks as though the cables just come straight down from the speaker sockets, giving the speaker socket (and the cable plug) the weight of the speaker lead hanging on them.
Now it may be the angle of the speakers, but they appear to be a bit skew-wiff on their stands. If so, if could be that their top-hats are too large for the diameter of the stand/tripod poles. If this is the case, then consider adding a layer or two of tape to the top of the poles. This will make them a little thicker and thus aid the speaker in sitting securely and upright on the tripod.
With regards to table layout (and I appeciate that the table looks as if its just what was around on the night, I'd definately suggest dropping the blue controller down onto the tabletop rather than balancing it on top of the systems case. One slightly sozzled Sharon and the controller heads towards a full width of mixer controls, probably shearing off the odd CD-deck jog-wheel on the way down. Also, and probably more important - I'm assuming that you took the photo with the camera at head height - if so, look how much audience the controller will block out for you (when they're there and dancin'. And if you cant see them....they cant see you...
If you were looking for some constructive critisism on what to buy next, then I would be hard pushed to find anything actually "wrong". If, however, you were wondering on area's of improvement, then I'd say that you need to think about what the audience see's when they look AT your show. At the moment its "presence" is quite low-key - but at least its not "industrial". Some shows can look like a hard hat zone.
Consider making fuller use of the UV tube at the front - super cheap option (real Blue Peter stuff this)...get a couple of UV Security marker pens and draw about 100 "stars" (about shirtbutton sized) onto that cloth you use. Instant UV starcloth !!! for £4
Slightly more upmarket would be to add some UV reactive lettering to the front of the cloth (with or without UV stars - from above suggestion) - your name in lights for about £1 per letter.