1. Attach the text area down using the css fixed so that it is always on top even by scrolling style whatsapp;
2. Allow everyone to enable or disable notification of a new message sound/vibration through maybe a menu icon gear positioned at the top right;
3. Allow sharing images via IM via the function attached files;
4. Enter the chat menu to attach emoticon/smiley style whatsapp;
These are my suggestions, I apologize for my English not very fair.