Irish international Finn joined the Tigers in December 2013 from Featherstone Rovers, for whom he scored 1,484 points in two spells at the club.
He has Super League experience under his belt already, following a spell at Wakefield a decade ago.
The half back made history in the sport in 2012 whilst at Rovers, setting a new world record of 41 consecutive goals, beating Barry Eaton's record of 38 in a row in 2003.
He proved to be a revelation in the halves during his first season back in the top flight, forming a formidable partnership with Marc Sneyd as Castleford reached the Challenge Cup final.
Liam is sponsored by Hutsby Potato Merchants
*Photograph courtesy of SWPix.