I talked to someone from StageCo at the old StageCo site in Werchter, where I took most of the pictures, and he confirmed that it were parts of the Stones stage. The stage(s) had been up at the StageCo site in Tildonk (NOT on the festival ground!) for most of the week and a guy who works at the firm right next to StageCo had seen a test picture on the big screen. Unfortunately, I was informed to late to see the stage in all it's glory....
And yes, the last three pictures are the Robbie Williams stage they are building at the StageCo site in Tildonk.
The stage being in Belgium does not mean a thing, as has been said in some postings; StageCo is doing the steelwork and they probably just tested it out after the long trip from New Zealand to Europe.
At Tildonk, they weren't as nice as in Werchter, and I was chased away. (and almost had to give them my camera), but that was probably because of the pics I was taking from the Robbie Williams stage. I just drove my car right on the grounds, so I WAS trespassing
However, on the way out I did see a lot of trailers with a sheet saying "Brussels" on it. (which still means nothing because I couldn't stop and take pictures to see if it looked like the Stones Stage)
Chris from Belgium