Is it possible to put in a standard Challenge message in? like everytime you challenge someone, that message will appear?
Yes and no. Currently there is no way to "set" the message in your preferences. But if you type a message at the beginning of your session, the application will remember that message for the entire session.
In the same train of thought of the challenge box: How about we actually be able to see the lvl of the person that challenged you? So ya know if you really want to bother accepting or not.
I asked for that before, but i have found that keeping the players' level a mystery makes it more fair and supresses prejudice :), you can look up the player by nick in the rankings anyway, so it's not a big deal..