The following effects are available in ExtraFireworks by default. You can configure more image-based ones and modify which items are used for crafting firework stars.
Display the text of a name tag on firework explosion.
Display the text in a box.
Display the content of a map via particles. Especially cool if players build pixel art on maps or if some form of map image plugin is used!
Player face and head
Display a player's face from a skull (or if using the box modifier the 4 sides)
A colorable fountain effect.
Three different level of snow fall particles.
The explosion is mainly useful for a louder “boom” sound, the effects are rather minimal.
You can also setup custom effects that can be crafted with other items which then use images to define how to display the particles. See the config for more info.