I have to jump in here now.
To the original poster: If you are going to "tip" I don't think it would be appropriate to leave a candle ea. day. You may have the same mousekeeper everyday, and who wants several candles, (I'm assuming they are the same.) I would maybe tip a small amount ea. day and find out how many different mousekeepers you've had during you stay and leave a candle for ea. of them, by name, if possible, at the end of your stay.
That said, I don't think that it is necessary to tip housekeepers in hotels and honestly, I usually don't. We occasionally do when the housekeeper has done something for us over and above the the normal things she/he is expected to do. I totally agree with BobC on this, it is not considered a tipped position and personally I get tired of lots of people who don't make that much less than me sticking their hands out for tips. No one tips me for being a good mom, or my husband for giving someone a job. This is not sour grapes, just the plain truth of the matter.
BTW, just to add to this thought, I NEVER base the amount tip that we leave a wait staff person on the amount of the bill. We base it on service, # of tables, how long we've been in the restraunt, and figure out what feel the server's time is worth based on how we've been treated and tip accordingly. If it is really good service, that amount will much more than 20% of our bill as we often share meals. I think if more people based their tipping on service and common sense, rather than what some "industry standard" is, then service would improve in many places. Now, I'm prepared for the negative comments that I'll receive from all the servers out there, but that's the way I feel.