Quark and ExtraAlchemy both add a number of potions. Sadly, neither are compatible with Rustic's much-cooler-than-vanilla alchemy system.

What would probably be ideal is having a system by which you can generate custom elixirs based off existing potions in a config, something like...
(forgive the horribly incorrect formatting)
Custom_Elixirs: {
[namespace:potion_name, namespace:ingrediant1, namespace:ingrediant2],
[etc.],
[etc.]
}
And it could check the given potion and automatically generate a texture based off the colors used in the potion's texture (i get that this part may be a lot of work, alternatively maybe a color hex code could be included in the config after ingrediant2 or something)