Flat as a pancake (no pancake images)
Flat tire (I have lots of car images but they all have fully inflated tires)
Musical flat (this had promise)
Flat line (just plain morbid)
The Earth is flat (I do have a map of the earth background image)
In the end, I just decided to make a seriously flat, one layer card. No embossing, heat or dry, just stamped images. I selected flowers from various stamp sets and stamped them in red, yellow and blue. The leafy image is the fern from Stampin' Up's Butterfly Basics set and stamped in green. A thank you sentiment in black and a quick clip of the lower right corner and the card was done.