Ok, I've gave it some thought, but i still need a person, action and object for U, X and Z!
(In case your wondering, I go up to the letter 'Z' because Upper and Middle layer are letters A-M and D layer is S-Z)
Persons:
Uma (Thurman)
X-men (any of them)
I also like Zeus, go with what Mats said
Actions:
U: to use, to un-anything (unzip, untie, undress, etc.)
X: don't use a verb that starts with X, but use things that are eXTREME! That's how I handled my one syllable X words, see my page here
www.speedcubing.com/chris/memo-words.html and look at the entire section for letter pairs starting with X. These words are all either eXtreme or taboo things, and that lets me know that the image is an "X" image.
Z: zap (as in shoot with a beam of something, laser beam, microwave beam, etc.), zip, zigzag, zero (as in to "zero in" or focus intensely on something), zoom (as in to zoom in, kind of like to zero in), zone (as in to zone out, or lose focus)
Objects:
U: Umbrella, underpants, umpire, etc. etc.
X: xylophone, x-ray machine, x-ray goggles, or go with the eXtreme idea and make the object something very huge or extreme or also maybe taboo
Z: zebra, zealot (the sham-wow guy for example), zuccini, Zoe (if you know a Zoe), Zombie, Zepplin
Chris