A company called PhotoStamps now allows you to put a photo or company logo on the stamp. It appears that the cost per stamp is the regular 37 cents.
Note: Although not directly related to patent law, I thought this was really cool. At MBHB, we already have a big stamp machine and postage paid envelopes, but this might be most useful for small firms — a way to customize your envelopes at a low cost.
Update: The cost is actually quite a bit more than 37 cents per stamp. The actual cost is $16.99 for 20 PhotoStamps plus shipping. This results in a cost of about 85 cents per stamp.