Vegas deigned not to give us a full alphabet with with to build signage, so I ripped apart some of the signs they did give us into separate letters with which to spell out the words of your dreams.
I got at least one of each letter, with the exception of Z. I didn't see any signs containing this letter. You can make a Z with a sideways N if necessary.
The only numbers I got are 2 and 1 from the Vault21 sign and 3 and 8 from the Lucky 38 sign.

1.2 - added the letters from the Silver Rush sign, + the frame. Also fixed a couple letters and made it so you can't see through the back of any of them.

1.1 version includes separated letters from Westside liquor store sign, so you have a Q now.

Other signs used:
Michaelangelo's
Bison Steve
Mojave Express
Freeside
Probably a couple others I forgot

I may do some more later, if I feel like it.

Not yet tested in game, haven't had time, but I figure you guys will do it quicker than me and surely let me know if there are any issues. They place fine in GECK.