I think for version 1.0 a standard icon set is fine. Two things though...
1) We may eventually want to make the icons customizable. Allowing people to build theme's, while not exactly practical, seems to encourage people to continue using your product even though they're getting bored and want to try something else.
However, this is probably still up for debate.
2) We will likely want to make the Toolbar's user changeable (as in you can add and remove icons to perform various actions). These actions could be a static set list, or better, in the same way that we plan to allow users to write plugins to perform actions, or add shortcuts to perform actions, we can allow users to add toolbar icons to perform actions. (Edit: I started a thread on another way of thinking about actions and the scripting system. http://forum.emeraldeditor.com/index.php?topic=238.0