A new Yafaray contest will be announced soon.
There is a voting thread for the contest topic open now.
Options include:-
Vintage machines and devices
Warrior Insects
Weather SFX
Technology wonders
Amazing Architecture
You can vote for the two that interest you most, and voting is open until Tuesday, 20:00 GMT.
You can use any version of Yafaray with any version of Blender, though the 2.5 exporter is not yet complete.
Here for more details:- http://www.yafaray.org/community/forum/viewtopic.php?f=15&t=3787