@ Heides, your range is 0xF8000000 to 0xF803FFFF
There are lots of technicalities to the way the game interprets meaning to the IID of a texture, but to be honest most of them don't seem to have any practical effect in the game that I have ever seen. I think what Barby is referring to is the "5th digit" (reading from the left) wealth indicator. This certainly has an effect, and should only be used if you want a wealth dependent texture. (A 0 in this position indicates no-wealth, 1 is low-wealth, 2 is medium-wealth and 3 is high-wealth.) To be safe, only use 4 to F in this position.
btw, the range you requested is the 56th one next in line, and at the current rate of allocation would not have been given out until sometime in April 2012!