I'm not in favor of the phrase "pork-barrel" spending. I just think it sounds too tasty. I understand that it's actually an old pre-Civil War custom where owners would give their slaves a barrel of pork and let them fight over it, but to me it seems like the sort of thing that I would eat at a Renaissance Fair (apologies, Renaissance Faire). As in, "whenever you've finished your honeyed mead, Jim, I'd like to go and get some rinds out of the pork barrel before the joust." It could even be the name of a really good backwoods BBQ joint, The Pork Barrel, famed for its unbelievably juicy ribs and how the log floor creaks alarmingly when you walk on it.
The sign would unquestionably be a picture of a pig with a barrel for a midsection, and the pig would have cartoon eyes and be smiling.
Update: I found a Pork Barrel Restaurant, but unbelievably, it serves seafood and seems to have no sort of homegrown charm about it.