ContatcsIf you look at this thread, you will know which contacts will layer and which contacts won't. I already have a huge list. The david skin is listed in post four and the contacts are listed in post three. You'll need both posts.
http://www.gaiaonline.com/guilds/viewtopic.php?page=1&t=17843259#221506013(I haven't updated it yet. If contacts were release in the last few months, they're not listed. If you know of contacts that I don't have listed and you know their layers, please tell me. :3 I will update the thread, but just haven't gotten to it yet.)
Tattoos The david skin should not have any layers on it that unequip tattoos. In my experience, all tattoos will layer with the david skin.
If a tattoo sits in the same area as the eyes (eye stripe tattoos), those tattoos will layer over the skin and under the eyes. The eyes aren't just drawn onto the base, they're like a having a pair of contacts on. The eyes include the grey eyes and a circle of white around each eye.
MouthsI'm currently writing a guide on skins. While writing it, I've realized that I need to make a guide on mouths too. It'll just be a quick guide on what layers the mouths sit on. I've bounced the idea around for a while... but now I've realized that I do need a mouth guide because just saying "mouth" is too general.
Anyway, the masterpieces comes with its own mouth. Because of that, mouth items will be unequipped if they're also on the mouth layer.
Mouth items that will be unequipped: Trick or Treat Tote mouths, knocked out teeth, both sundae sweets, lips from the Hidden Ace, kink's reprise smile, everyone's reprise smile, (i'm pretty sure the dandy reprise's smile too).... and many more...
Items that look like mouths, but layer over them, will equip with the david skin.
(Here is what I mean. On the equip screen, you used the big giant open mouth default expression. If you equip any of the items above, that expression is hidden. If you equip any of the items below, that expression does not disappear. You can have a big gaping mouth with buck teeth sticking out of it. These items layer above mouths. (You can also equip any of these items over the items I listed above.)
Items that layer over david skin: buck teeth, vampire's fangs (rawr, and the other three poses), puppy mask.
AND OH MY GOSH! I just tested this to make sure, but the layers have changed. x ----x; The buck teeth and vampire's fangs are layering below the mouth items. I don't know whether the layers changed for everyone or whether the mouths just layer weird for glompie bases. u .u;
Edit; I made this post last night at 4:41 am, so I've edited it to make more sense. It said the same thing before, but not as concise. I know, this still isn't very concise. Oh well. :}
After I made this post, I edited it and said that I'd go make the skins guide visible. I had it hidden while working on it. I'm still in the process of editing and formatting, but maybe it'd help. For the david skin, it says pretty much the same info the contacts thread does since I copy/pasted it. It's in the guide forum now, so you can look at it too if you'd like.