Avaz does not support Sign Language directly, however you can use some symbols from the in-built library
Avaz uses the Symbostix library of images for the picture mode. The Symbolstix library has a rich content of 40,000+ symbols, of which there are approximately 600 symbols to denote Sign Language and you can use any of these symbols as images in Avaz.
E.g. here are some examples
Close Friend More Stop Thank you
Click here to see How to add image or change the image