That Edit Icons page could have - above and below all tick boxes - a general tick: a click ticks all tick boxes (useful if you got over 300 smileys) and a second click unticks all tick boxes.
And instead of just one tick box beside each smiley, it could be three:
- one to tick/untick just this smiley
- one to tick/untick this smiley and all others above
- one to tick/untick this smiley and all others below
This makes sense if you have larger numbers of smileys.
And all available smileys could, instead of being listed beside the message box, be listed below the message box. This looks better if a person has more than a certain number of smileys enabled. Or they could be inside an area not taller than the message field, and have a vertical scroll bar. Please see the screenshot: