Many thanks to Tartalla (Linda Thompson) of Legio XX

Salve: I found some examples of genuine Pompeiian graffitti (all attested
to in Vol. IV of the Corpus Inscriptionum Latinarum -- the number after
each graffitto gives its citation in CIL v. IV) that you might want to
scribble on the caupona walls. They're in no particular order. Punctuation
has been modernized. ** Linda Thompson (Taratalla)

*Scripsit Aemilius Celer, Invidiose qui deles, aegrotes. (3775) --
Aemilius Celer has written: O you jealous man who erases this, get sick.

* Perarius, fur es! (4764) -- Perarius, you're a thief!

* Samius Cornelius, suspendere! (1864) -- Samius Cornelius, go hang!

* Urna aenea periit de taberna. Si quis rettulerit, dabuntur HS LXV.  Si
furem dabit, unde rem servare possimus, HS XX. (64) --
A bronze jar has been lost from the tavern. 65 sesterces reward
for whoever returns it. 20 sesterces for information leading
to the apprehension of the thief and the recovery of the jar.

* Livia Alexandro salutem. Si vales, no multum curo. Si perieris, gaudeo.
(1593) -- Livia to Alexander: hello. If you're well, I don't much care. If
              you die, I'll be happy.

* Victoria, vale! Et ubique es, suaviter sternutes! (1477) --
   Goodbye, Victoria! Everywhere you are, pleasant snores!

* Stronnius nil scit. (2409a) -- Stronnius doesn't know anything.

*Ladicula fur est. (4776) -- Ladicula is a thief.

*Serena Isidorem fastidat. (3117) -- Serena despises Isidorus.

*Accepi epistulam tuam. (5031) -- I got your letter.

* Fures foras; frugi into. (4278) -- Thieves outside; honest men inside.

* Otiosis locus hic non est.  Discede, morator! (813) --
   No loitering here. Take a hike, lounge lizard!

*Salve, lucrum! (874) -- Welcome, wealth!

*Cedo, ceneamus! (878) -- C'mon, let's eat!

* Admiror, paries, te non cedidisse ruina,/ qui tot scriptorum taedia
sustineas. (1904, 2461, 2487)  -- Wall, I'm amazed that you don't fall down
in ruins from holding up the silly scribblings of so many writers. [Note:
this is an elegiac couplet -- dactylic hexameter in the 1st line, &
pentameter in the 2nd.]

*Thraex est suspirium puellarum. (4356) -- Thraex is the girls'
  heart-throb.

*C. Cuspium Pansam aedilem aurifices universi rogant. (710) -- All the
  goldsmiths ask [you to voite for] Gaius Cuspius Pansa [as] aedile.

*C. Iulium Polybium IIvirum muliones rogant. (113) -- The mule-drivers ask
  [you to vote for] Gaius Julius Polybius [as] duovir (mayor).

* Vatiam aedilem furunculi rogant. (576) --
  The petty thieves ask [you to vote for] Vatia [as] consul.

* Hic venatio pugnabit V Kalendas Septembres et Felix ad ursos pugnabit.
(1989) -- Wild beast hunt on Sept. 9th -- Felix will fight bears.

* Rusticus Malius: pugnarum XII, coronarum XI. (4302) -- Rusticus Malius:
   12 fights, 11 wins.

* Miximus in lecto; fateor, peccavimus, hospes. Si dicis quare, nulla
matella fuit. (4957) --
   I peed in the bed. Landlord, I admit I did wrong.
   If you ask why, there was no chamber pot.