In the Pipeworks mod there is this feature to craft oil out of leaves and process it to paraffin in the furnace. I would totally love it, if you would bind the crafting of candles to that paraffin (therefore making even organical renewable candles...). :)
As the step before is Oil, you could even add an oillamp. I thought about the following recipe:
clay lump|clay lump|empty
clay lump|empty |clay lump => 6 raw clay oil lamps
empty |clay lump|empty
=> processed in the furnace => empty oil lamp
empty oil lamp | oil | cotton => oil lamp
Or additionally:
empty | cotton | empty
cotton | empty | cotton => hanging oil lamp (for ceilings)
empty | oil lamp| empty