I had the same problem you did, trying to put several different tiles on the same matrix. I couldn't figure out to SET MATRIX TILE for more than 1 tile, so I was forced to create an image with several different textures in 1 bitmap. I created this simply with PAINT. I copied and pasted several images into 1. All the images have to be same size, unfortunately. If you need to change the size of 1 texture, just go to Image on the menu and click Strech/Skew or just type Ctrl+W. Then change the vertical or horizonatal percent under Stretch. I assume you understand percents, but if not, just leave another message. Hope this has helped you.
don't re-elect bush