I highly second the Candle Lanterns, the ones with the spring doohicky that keeps the candle in the proper position as it burns "down", and has the glass sides and compacts down into itself. Great great things, have used them for ages and ages. We have a few tents in the family, and in my "candle lantern bag" I have spare candles, matches, the circular reflective thingee to bounce the light downwards, and most importantly, a coiled up bit of thin wire that I hang the candle lantern from either a hook at top of tent, or if there is no hook, from a string that is permaenently attached to our tents that dont have hookee things.
Candle lantern then hangs down from middle of tent, not too close to top of tent, can be bumped into and doesnt fall, and it really really takes teh edge of cold and damp off the inside of a tent. No, I dont sleep with them on, but then, if secured properly (use common sense) it would nt be a prob, and even if it fell, no open flame is there--YES it would melt your sleeping bag cuz its hot, but honestly, they work great.
Have used them for well over 20 years if not more.
this of course will not "heat" a tent at below freezing, so I second the winter hat or toque as we say here, a real warm one, Neck ups etc etc
Polar fleece pants, wool socks, you name it, go for the light weight highest insulation stuff--fleece being great.
+2 on the good camp mat or TWO. Do you have a down vest? great warmth vs weight.
chemical warmers? what the heck, why not, small but could make a nice diff in your sleeping bag.
Mitts!!! liner mitts or liner gloves too.
dry soup packs....hot luiquid makes a heck of a diff of how one feels. More food too, cold weather means you'll want more food.
would be best if you could try out stuff beforehand.