look in the ebebank/_builder folder.
The brushes are editable in a text editor by replacing the 0's and 1's.
0 for no piece and 1 for a piece to be there.
Define the dimensions above for the size you need. Depth does not seem to work completely yet. Give them a new brush name for later use.
To change the textures, edit the .png and .dds files to what you want. I am guessing that there is only one texture pallet right now.
Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz, 2400 Mhz, 4 Core(s), 4 Logical Processor(s), 8gb RAM, Nvidia gtx660, Windows 7 Pro 64bit, Screen resolution 1680 x 1050.