Next / Prev and looping/cycling entries instead of reaching the end of the selected results Is there a way to be able to use entry.getNext(params) to return back to the first entry when you're viewing the last entry in the parameters?

With the result of looping/cycling through all entries and returning to the original.
If there isn't a "next" sibling, entry.getNext() returns null – in which case you can use Twig's default filter to set an alternative value (i.e. your first entry).

Untested, but something like this should work:

{% set nextEntry = entry.getNext|craft.entries.section('mySectionHandle').first() %}