In the most recent update of the Dalek Mod we added Chalkboards. As you should know there is a "Blob" option which allows you to convert your drawing into a string of text and copy it onto other chalkboards. With this little tool you can convert any 32x18 image into a blob to be used on the chalkboards
Just double click on the jar and then click "Open File". Next find the image you wish to use and press open. Once the image is open you just have to press "Generate Blob" and in the text box to the left your blob will be generated.
At the moment no. As it currently stands all images have to be 32x18 pixels in size. If you try and open a larger image it will tell you that the file is too big and will not open it.
(Works on Mac, Linux and Windows)