I think it's quite difficult to judge these without seeing at least a basic color scheme/layout of what the new theme on the forums is going to look like.
That said, I'm puzzled as to why something along the lines of what we see in the AVS logo at the top of the screen wasn't suggested. The odd gold color of the AV and the dull-ish prism colors streaking off does look like something out of the 70s, like an intro logo you'd see on a late 70s or even early 80s or 90s educational VHS. But it fits you know, it grows on you. The logo seems to fit perfectly with the 1995 start date of AVS. Makes me want to hear that strong voice say VIACOM and a cheesy wooshing sound and synth tone as a logo comes in from the corner of the screen. Sorry got lost in nostalgia for a minute!
Yeah I think something like this would have done great as a default avatar:
However I did cast my vote of the 5. I didn't expect so much back and forth of thought on the matter. I wanted number 1 originally because of the modern look. I wanted to choose number 4 afterwards because of the flashy yet easily fallen into the background colors. But I unexpectedly decided to go with number 5 because...well I don't really know why, but I suspect the darker RGB and the duller-ish feel to it reminded me of the AVS logo.