No, I haven't forgotten that I had started a "series" of posts about lucha libre masks; I've just been busy. I thought I'd spent this post describing some things that aren't immediately obvious about lucha libre masks, at least based on my experience.
Sizing
Mascareros have a notion of a standard adult size for masks. As far as I can tell, this standard size is consistently roughly aimed at what we'd consider in the US to be a head size of around 7 1/4 to 7 3/8 or so. My size is around 7 1/2, and every "standard size" mask that I have fits, but usually just a bit snugly. (I usually do order standard size, though, just because it's easier and more likely to be on hand. I do have one mask that was measured at 1 cm larger, and it fits more naturally.) This means that if you wear, say, size 8, you'll need to make special orders. :) Also, lace-up masks will obviously have a little more leeway than masks that are closed in the back.
As far as neck size goes, my collar size is 16", and, again, every standard-size mask with snaps or Velcro fits snugly, so take this as a sign that if your neck is any bigger than that, you'll probably need a larger mask around the neck/chin. Masks with a single piece of elastic around the neck have some stretch room to spare for me, so you might have more leeway with those masks.
Laces and display heads
Some mascareros will ship laces with lace-up masks; others don't and expect you to buy laces on your own. Amazon.com is a good place to find laces of all sorts of wacky colors to match masks. Length will obviously depend on how many eyelets the mask has and how tightly you'll be able to lace to mask. For a point of reference, Deportes Martinez masks have 14 pairs of eyelets in the back and ship with 60" laces
If you want to put masks on display, you can get mannequin heads made out of styrofoam or plastic on Amazon as well. I bought these for my office: http://www.amazon.com/gp/product/B000V9PYHY/ref=oh_o00_s00_i00_details
They're significantly smaller than an average human head, but they serve their purpose well enough, and are fairly inexpensive. My only real complaint is that they're so light that it's a bit difficult to keep them in place while trying to get a closed mask with an elastic neckband on them, so maybe next time I'll try to find something a little bit heavier and/or larger.
Next post, I'll start actually talking about specific mask vendors.