a nice trick to add a 3d look to the bricks is to make a few small changes:
1.) paint the upper and the left side with a small white (1-2pixel and opaque) line ...you can use the dodge and burn as well for this
2.) paint a bigger small line at the bottom and right side of one brick to simulate sunlight
3.) paint a small burn slope onto the brick. start at the upper right corner and move to the lower left one...not linear but make a small bulge into it. this will add some depth to the brick.
4.) overlay the brick with a grain texture or a artistic layer (use multiply and lower the alpha to 10%) to add some randomnes to the brick.