An idea to implement:
https://en.wikipedia.org/wiki/Unrolled_linked_list
See e.g.:
http://www.sanfoundry.com/java-program-implement-unrolled-linked-list/
I'm not sure how often ULL are done, say in C, as they are harder to implement, and C is not a generic/type safe language.
I support Julia, being an array-based language first, not List-based as in Lisp, as they are faster as the general data structure [for some things, know O(1) for list that would be O(n) for arrays]
I do wander why lists where left out in the Julia standard library (I guess, because someone like you cn make their own), with the default collections often ok. What was your motivation to do lists? Or was it maybe just a Julia exercise?