It can be quite annoying having to choose between an amazing looking backpack with none/no useful abilities and a backpack that doesn't suit you at all but with a really good ability.

It would be great to be able to choose a cosmetic override for the equipped backpack to not miss out on the usefulness of the backpack ability while having the perfect looking backpack that suits your character.

Could be done via a button in the backpack interface with a list of backpacks to choose for cosmetic override.
Alternatively could be done by consuming the desired cosmetic override backpack.
(Of course could have a config line to allow players to change the cosmetic override)

Personally I feel it would devalue the special backpacks a bit.
Being able to dye regular backpacks allows the player to personalize the backpacks already, offering the cosmetic side of things. Doing so to the special backpacks removes unique value.

Example

• Ender Dragon backpack being able to look the same as Blaze backpack removes 1 part of the special backpack which then only leaves its ability if offers as the only reason it is special. At that point why couldn't a regular backpack have special abilities? (not saying they should just trying to prove my point)

If added I would hope its something I could change in the config at the very least.

Theres a "skin" slot that accepts another empty backpack and applies it as its texture?