Depends on how you're doing it, and what sort of mat (material) you're using. There are some brick wall mats out there (check freebies, there's loads of mats there).
First, see if the texture is just the overal color of a brick, or actually has the mortar pattern on it as well. Sometimes you can change the way the mat looks by going into the Deep Texture Editor (even I don't completely understand it..;). Click on the 'm' next to your object or boolean, and look in the window on the upper right side. You should see some settings there. Without selecting anything, look for a setting that says 'world space, world cubic, etc' (It's one of the round buttons, but I'm at work and don't have Bryce in front of me). Sometimes selecting 'world cubic' will make the pattern smaller and more detailed looking.
hope this helps.

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)