David Lee Roth wearing nothing but socks
A very large black light cannibis sativa leaf
And a beach scene with a seagull and the “If you love something set it free” poem…
Thanks for the laugh and the trip down memory lane
Zappa on the crappa. Got it when I was 13 and it was still there when I moved out at 18.
I didn’t do the poster thing, but my older brothers did. I would sneak into their room to listen to 8-tracks and put on the black light.
They had Trickey Dick on a motorcycle.
But my favorite was two buzzards and one says “Patience my ass, I’m going to kill something”
drat, gonzoron beat me to it, I was gonna say “FCM is one of my favorite posters” but now I won’t, since the joke has already been played.
In college: Earthrise over the Moon (Apollo 8?)
A smallish poster of a smog cloud over a generic cityscape, with a waving hand sticking thru the smog, “Pollution is Nature’s Way of Saying Bye-Bye”
A black-light Taurus (the astrological sign - the car was decades away).
My FIL was a big Farrah fan, we got him The Poster for a birthday or Dad’s Day or something.
A friend had “Fly United” - not an airline poster, but two geese.
Not from my youth, but I was younger - about 15 or 16 years ago. This was at work before they started cracking down on sexual harrassment in any possible form. I had a poster from the Chippendale series - a very attractive, sandy blonde gent standing in what was obviously a tiled bathroom wearing only a red towel. Goodness gracious, what a fine looking specimen he was!!
Shortly thereafter, I found another poster of a man in a white towel and a woman’s hand reaching into the frame to remove it. I had them hung on the wall of my cubicle - mainly to torment my somewhat arrogant ass of a cube mate.
One day, I came to work to find a pink balloon (like one uses to make balloon animals) inflated and taped to red-towel guy. Cracked me up!!! Sadly, it was only a few months later that the hammer fell and I had to take my posters down. Sadder still, they were crushed and torn in a move.
The most memorable poster on my wall was one of River Phoenix. It was a movie poster from “A Night In The Life of Jimmy Reardon”. He was wearing a plain white t-shirt, and a pair of jeans. He was standing against a red background.
It was the hottest picture I’ve ever seen. I still think about that picture sometimes. I wonder if I still have it somewhere…
Oh, and I had the prerequisite Duran Duran poster. It was from the “Wild Boys” video.
I had an entire wall covered with black light posters. Back in the '70s we all did. Also had the requisite bird flip from Easy Rider and an armadillo humping the state capitol with the caption “Cross-breeding”. Looking back I can’t believe my conservative parents condoned such. There were a few up by M.C. Escher as well.
I had the 5 foot X 3 foot poster of Wham! It took up and entire dorm wall.
I also had the Chippendale’s B&W poster - of a man stipping - with the caption “All men are not created equal.”
And various concert posters… Adam Ant… David Bowie…
(Damn I’m Old!)
I had the aforementioned Farrah in the red bathing suit, Cheryl Ladd in a wet bathing suit, and the pride of my collection, one I’d inherited from an older brother. It was a lavish, beautifully done drawing of all the Disney characters frolicking at Disney World, in various states of undress, and doing everything they could to destroy the innocence of Disney. Blow jobs, bong-hitting, every position imaginable for sex involving evey manner of being… and I’ll never forget Tinkerbell, the image of her is burned into my mind forever.
Most of mine were horse pictures and posters, I really was a horse-crazy young girl. I had this huge one of a herd of wild horses, it was about 3’x5’. I wish I could find it again, I had many fantasies of riding those mustangs.
Then when I hit 14, I got a David Lee Roth poster in a Van Halen album, and put that up. That’s when all the trouble started…
My younger brother had the Farrah poster.
I had a poster of the cover art from *Peter Wolf’s - Up To No Good *(See it here. I’ve never heard any of his music, but with a blonde like that who needed music? )
I also had various Battletech Mech blueprints (big poster sized rigs, really cool!) and that’s about it really. 5 Mech blueprints take up a lot of wall space.
Yes, I was a geek. If the big mechs didn’t give it away, the cartoon chick would. 
Now I have a Fox Mulder’ish “I want to Believe” poster at work.
Had a couple of Garfield ones when I was little.
In college, though I went kinda nuts:
World map (political)
World map (nighttime satellite photo)
Map of medieval England
The Gashlycrumb Tinies
The Final Exam (Medicine: Remove your own appendix)
Albert Einstein’s tongue photo (with anti-war message)
Pink Floyd’s The Wall
A poster of Hell that looked liked a cross between Hieronymus Bosch and Peter Max. Sickeningly cool.
Akira (the movie)
plus a few I’ve probably forgotten
I’ve always wanted one of these. Not the illustration version, but the photo, taken sort of from above, I think.
That would be the Disneyland Memorial Orgy.
When I was 14-18, my bedroom walls were covered with very closely spaced posters, art postcards, paintings and poems from what would have been dado rail height (if there’d been a dado rail) to ceiling height. My favourite poster was an enormous Cure one. Three full page pictures of food from Marie Claire magazine have gone into cheap frames and made it onto the walls in my house here and now, ten years on. Marie Claire used to have the best food photography.
Map of World, Map of the USA, HUGE Led Zeppelin poster at least 5’X5’ of the cover of ZP II(I NEED to find that, it would look great in my bar), the standard LZ poster of the guy with lantern standing on the mountain, several Aerosmith posters, a couple of 3rd gen RX-7, a St.L. Cardinals 1982 Pennant and a picture of Ted Williams and Joe Dimagio together. Oh and a Brendan Shanahan poster.
[sub]some of these weren’t up at the same time others were but they all spent a good long while on my walls at different times in my teenage years[/sub]
I have to say I’m really surprised no one else has mentioned travel posters. I figured they were pretty common and boring. Maybe I was more innovative and daring than I thought?? 
No, You were just too cheap to go out an buy posters and was satisfied with travel angency trash.
Another poster I had was a really large solar system map.
Most of my posters were of rock bands (Iron Maiden, Ratt, Def Leppard, Scorpions, etc.) I also had a couple of sports car posters to vary the theme. I had several other odds and ends to fill in the smaller spaces. Sometimes I would just take a page out of one of my Hit Parader or Circus magazines and put it up. I never had any bikini-clad women on my walls since I didn’t think my parents would appreciate them.
For some reason I did have that poster. Strange thing for a little girl to have on the wall, but I had it.
Two of my favorites:
One was a large (5’x3’ ish) map of the solar system made back in the late 50’s, early 60’s. It had little panels on each planet, illustrated. Yes, it was all “jungles of venus,” “canals of Mars” type things. Yes, the people who made it were serious. Very cool.
Another one was a scenic view of a rocky shoreline in Newfoundland. In the foreground, facing away from the camera was a man in a trench coat. The trench coat was wide open. Across the bottom of the poster were the words “Expose Yourself to Newfoundland.”