In reply to Ian Campbell:
Before I went off to uni I just emailed a load of companies asking for posters and stickers, got a surprisingly good response.
Lowe Alpine, Haglofs, Petzl and Berghaus were particularly good, giving me some huge wall posters and other stuff, all for free. Patagonia, Mammut and Arc'teryx all sent me a load of stickers, but sadly no posters.
Got to be worth a punt!