Mostly10 CREATED A CONVENTION CLOTHING GUIDE!
I was super thrilled, because I knew full well that Jared likes to steal Sam's clothes and wear them out in the wild. So, thanks to mostly10, you'll now find an additional fact listed at the bottom of the entries to some of Sam's shirts in my Clothing Catalogue.
Of course, I went through and picked out Sam's shirts very very late Sunday night when I should have been sleeping (...so sue me, I was excited), so I could have mis-identified some things, but hopefully if I did, people will let me know.
Unlike a lot of fans, I don't actually collect pictures of Jensen and Jared*, so I ONLY had the pictures from Mostly10's guide to go off of...and some of them aren't the best for light/colour/detail. So, yeah, if someone has a better picture of a shirt out there and tells me I didn't identify it correctly, then I'm willing to believe that person. :P
Also, in 2009 Jensen wore a very Sam-like shirt to Asylum 3. It's not Sam's shirt...but it's the style he favours, so subtract the Jensen-beard and you'd get an idea about what Dean!Sam would look like in a bodyswap episode (or what the show would look like if Jensen had been hired to play Sam and they kept the wardrobe the same).
*the only "Jared and Jensen" pictures I have on my computer are screencaps for my own clothing catalogue...so, yeah, not very useful. I do have raloria's pictures from the two Vancouver Conventions that I went to - because I don't take my own pictures at that event, but that's it.