...and completed. Features:
1. Complete coverage of the interface - the only place you'll need see a script effect icon is on weapon enchantments.
2. OBSE .dll plugin that provides a few functions for assigning icons to spells. Usage is super easy:
SetSpellIcon MySpell "MyFolder\MyIcon.dds"
3. Mod file that assigns icons to 500+ scripted spells from Oblivion and various mods.
4. Well written explanation of how to assign custom icons to your spells, as well as use the extra convenience features provided by the .esm (file checks, .ini assignment).
Once I hear back from xilver regarding permissions I will release.