There was a wonderful forum thread of WoW motivational posters many months ago, but alas, it seems to have been lost to the ages. Luckily, a few of the fan-created gems seem to have been saved on the RPG Motivational Posters site. More snarky posters can be found beyond the cut.
If you'd like to make a poster, the motivational poster generator can be found here. Host your poster on photobucket or some such site and show us your work!