I made a design with a catchy slogan I came up with and used a photo I took of the flag at Liberty Island (where the statue is).
http://www.cafepress.com/Tax_Go
There are cheaper options than the national one. I didn't put local city/state though. (Hopefully to be generic for nationwide, and all year long).
The April 15 event for Tax Day is set to be #2 of 10 events.
Here's a parking map (including lot with black marker circle not pin-tagged) http://twitpic.com/2nuh4