rooms definitions: find a way to randomize textures on a tiled surface

[meszaros-lajos-gyorgy]

Using the same texture, even if it is seamlessly tileable, can look boring and arx has a lot of nice variations for certain blocks. Alicia's wall could be broken up by inserting the cracked wall variants occasionally to the flat white surface:

The texture randomization should be specified with percentages, for example use ALICIAROOM_MUR01.jpg 90% of the time, but use ALICIAROOM_MUR03.jpg for the remaining 10%.