What is the biblical basis for sects who believe in serpent worship?

There is not any biblical basis for serpent "worship".

If you are speaking of the snake handlers like these folk (http://www.aliciapatterson.org/APF001975/Peyton/Peyton04/Peyton04.html), then the reference they cite for what they do is Mark 16:18: "they will pick up snakes in their hands, and if they drink any deadly thing, it will not harm them".

There are some rarer cases in which some claim to ingest amounts of arsenic unharmed as well, though this is far less common. Though seemingly somewhat rare, nevertheless, I believe deaths have been reported as of snake handling in these acts.

If you really want to get deep into why people worship serpents or reptilians, read David Icke. He explains why there are so many statues with snakes and reptile on them from Egypt and other places.