how to antique poster paper

[rhinohumper.livejournal.com]

I have several reprints of vintage posters that I bought from art.com. Currently, they're in poster frames on the walls of my apartment. Needless to say, they look crappy. I'd like to antique them somehow, then paste them onto wood panels. My question is: Are there any ideas as to how to antique poster paper? The only technique I can come up with is soaking them in tea, but if you have any others (no matter how outrageous), please let me know.