Quote Originally Posted by max5212 View Post
The feat Spell Thematics exists for this purpose. It's a feat that lets you choose a theme, and apply that theme to any visual representation of any spells you can cast. Its only mechanical effect is increasing the Spellcraft DC to identify your spell by 4 and gives you +1 CL for 1 spell per spell level. Any other spell can be affected though, they just don't get the +1 CL bonus. It's not even considered a Metamagic effect, so it doesn't have a downside. You can't make a spell invisible with it.

This means a Fireball can be shaped as a bird that explodes in butterflies and crazy stuff like that.
I almost always let casters do that for free if they want, without any of the mechanical bonuses.