there are the brushtex, papertex, and blotmap folder for other imported textures for brushes,
there are a tool for making your own in folder
but you can copy bmp file and edit your own line dots and save as new and place in same folder,
chalk brush may be texture in other folder or in wrong folder,
you can search around for brushes and textures online and add to folders,
http://sai.detstwo.com/forum/index.php/t...
http://toadsdontexist.deviantart.com/art/9-Elemaps-for-SAI-287885853