I can see doing a few of these in advance at the beginning of the year as thank you's for presenters and field trips :) already ready to go! :) Or a wonderful Teacher Appreciation Card - using a thumbprint from each child to make the balloons! Love it!
Never, ever take your clients/customers for granted. Always show your appreciation for their business. The easiest way is to simply say "thanks." But do so with sincerity. In this excellent example (from a family-owned restaurant in Louisville), the industry-standard "Thank You" sign on the door is replaced by this incredibly personal & sincere note. What a wonderful lasting impression to leave customers.