Ever thought about creating custom fireworks? Now it's possible and not so difficult! Use your own patterns (images) to create new fireworks. You can also change the fireworks color and size!
Update: since I stopped developing Spigot plugins, ericgolde555 started ImageFireworksReborn (which you should use). Old Version: https://www.spigotmc.org/resources/imagefireworks.18932/
Spigot: https://www.spigotmc.org/resources/imagefireworksreborn.38203/ Github: https://github.com/egold555/ImageFirewoksReborn
/imagefireworks <give:launch> <player> <firework name>
/imgfws <give:launch> <player> <firework name>
/imagefireworks reload
/imgfws reload