What do they mean? There are many translations going around the Internet -- assuming that the pictures are real and that's actually Hebrew. You can find them at the link. Offer your own interpretations in the comments, because this 3PO-series droid isn't helping me one bit.
Link -via
io9
Eran Hadas (friends with Keren Katz) also commented on Keren Katz's photo.
Eran wrote: "Nicholas, the writing on the armor is unclear, but using some visual imagination, the letters might add up to say: "His actions are not forgiven until he has won."
LOTS of hebrew all over the various props, not just vader.
The most common line was "starwars l'ad" or Star Wars forever.
And for the record, the last line starts with an Ayin, not a Yod. It spells "Ad." (roughly: until) The word after that looks like "sh'zachah" which means something like "he merits it". I can't read the second line because it's upside-down and poorly pictured on top of that (even when I rotate, having trouble differentiating letters). First line starts with "ein" (which is a negative, depends on the verb after it) and is followed by a present-tense verb that I can't read because the letters are run together and the image is low quality.
the top line i can only make out a few letters clearly.
the middle line looks upside down.
the last line looks like it starts (hebrew reads r-l) with the word "yad", meaning hand.
boosting the argument is that yad is often used as the start of phrases/compound nouns like "hand of _____" and the fact that the letter patterns in all lines look right (words starting with the aleph character, silent vowels and consonants alternated, etc.)