Well, basically i places the image in a random template or inside a random ACTIVE post.. lets say in a post that has been posted in, in the last...5 days. That could also be chosen from inside the admin panel. But also a Random template, FAQ..Control panel..Forum home..etc..etc.. showthread.. those types of things. Then when someone clicks on it They are taken to a Congratualtions screen, and there is a Auto Thread generated in the forum of your choice and a PM sent to teh Administrators to give out the necessary reward.

The image might not look nice just smacked into a template, so maybe it should just appear in one of the corners, like bottom right or left.