I don't dream of mirrors too often. This topic made me curious, so I searched back through my entire dream journal to look for mirror references. This is what I found:
(from 'Garden of Doom')
The room I walked into was similar to the one with the box in that it had even more racks of pretty costumes, but it also had a mirror, and there were people in there!
(from 'Wonderland's Cloakroom')
I got temporarily trapped in one particular room crammed with equipment and lots of people. It was also pretty smoky (not cigarette smoke). In there, some women started singing along to music that came out of nowhere and tried to get me to sing along. I refused because it looked too embarrassing. But everyone in the room was doing it! Then a man who was sort of good-looking (he had Latin blood but had a bad hairdo of longish straight black hair) came over to me and sang the solo for the bridge about how sexy I was and all that stuff. I think he was trying to seduce me but instead I found it really scary. He was a good singer, but seemed really sleazy, and not genuine. He kept coming closer and I kept backing away until I backed into a clothes rack full of crazy fluffy hats. The women singing called out to me and said to put one on. I picked the most normal-looking one up, which was a fluffy top hat with thick black and white vertical stripes and thought it would look horrible with what I was wearing.
Just then, however, the smoke cleared and I saw I wasnít too far away from a full-length mirror. In the mirror I saw that the hat actually matched my bag, which was my black bag in real life with the addition of white stripes. I also saw that I was already wearing a pretty hideous outfit of denim and pink, plus a bit of a punk hairdo.
(from 'Mercenaries and Medicine')
Vet Miller put his hands on my back and did something to me that steadied my legs, but I still felt too out of control. I realised that I was looking at myself in his mirror Ė the pendant had transformed me into the strangest little creature Iíd ever seen. The closest description I can give is that I looked like a translucent blue horse-like creature, except more spindly and skinny than any real horse ever was. Long, feathery blue wings sprouted from my back which kept twitching slightly as I looked at them. In height, I didnít quite reach Vetís shoulder. I shook my head from side to side, and the mirror confirmed it. The thing in the mirror was very beautiful, but it was apparently me.
(from 'The Priest and the Swordsman')
Around the cart and the table, I found little pieces of glassy stuff, one by one. Most of them were very small, and I only noticed them because of the strange material with which they were made. It looked like glass and metal at the same time. My best description is of a piece of a mirror which at once reflected light and let it shine through transparently. They were all of a silvery-clear colour. All in all, I found about four little pieces which looked like nuts and bolts, a larger horn-shaped piece just a bit bigger than my long finger, and a smaller horn-shaped piece that faced the opposite direction. In addition I found some obvious pieces of jewellery made of the same material Ė earrings in particular.
(from 'Four Dragons and Palaces Galore')
The first area I came to was a dark little booth-like place full of hats. I remember thinking they had something to do with Gwen Stefani, for some reason Ė perhaps it was a fashion line of hers. I tried on a few, and they all looked fantastic in the full-length mirror without exception. The sort of thing one would wear to the horse races to show off, except if possible even more stylish. I spent quite a while in there, but I felt like I had no money to even think of buying something and so eventually moved on.
(from 'I am a Brat and Conquer the Aliens')
I canít remember the rest of the conversation, but at some point I looked in the window next to me and saw my reflection in it Ė I remember being very startled by how beautiful I seemed! The funny thing was, I looked just like myself in real life, which to me is not that pretty, but in the dream I thought I really did look just like a real princess, which is perhaps why I was so convinced I was one. I was no longer wearing the awful flannelette pyjamas, but instead some gorgeous harem-style outfit of blue, cream and gold. My hair was done half up in a way that made it cascade down in wild loose ringlets, very pretty.
I admired my reflection for a few moments, but was interrupted by one of my family members letting out a cry and pointing to a space behind me in the living room. Instead of turning to see what she was so scared about, I instead kept looking in the window so as to see the reflection of whatever it was, not the reality. And there, on the sofa behind me, was a man sitting down with a giant black fishbowl helmet on his head, looking directly at me.
(from 'Punk Princess')
But a moment later, I found out! My outfit began to change! I suddenly found that big black boots appeared on my legs Ė they were above knee-height and tied with thick black laces and bows. Likewise, similar long black gloves appeared on my arms, bedecked with the same laces. I turned to my reflection in the mirror and saw that my dress had completely changed as well Ė some of the purple still shone through, but mostly it had turned black. It was a lot less revealing now, with a high collar and covered shoulders. White bows were hanging off the sides in places. The front was done up a bit like a corset, but it looked very cool.
What amazed me the most, however, was my hair! It had turned pitch-black (which actually really suited me, because here my face did not look like it does in real life either), and about half of it had been plaited by Wendy into thick coarse tresses. Some of these hung down straight at the sides with the rest of my hair (which was quite short), but others had been twisted into small loops forming a crown shape on my head, and others still were positioned so the little tufted bits at the end stuck up in spikes.
It not only looked beautiful, but was extremely cool. Overall, it made me look like such a punk girl, bedecked in black leather and purple silk as I was, with bows and ribbons and laces everywhere! Even though I didnít feel like a punk, I was very impressed!
(from 'Journeys Turn Sour in Rigid Dictatorship Style')
There was something else about the book from my brother that I canít remember. It was magical in some way Ė I suspect in that instructions would appear in it as I needed them, but Iím not sure. Anyway, after I had finished reading it, and when I was brushing my hair at the dresser, I heard my brotherís voice coming from the mirror. I went over to it and saw my brotherís face through it. We had a quick chat, and he warned me of something, but I canít remember the conversation very well. I think he was held up and heíd be a while longer before he could rescue me. It made me feel confident, anyway, because the dictator clearly couldnít see what I was up to in my room, or he would have punished me, and he didnít.
...that's about all I could find, except for some very minor side-references.