Stay Palm is a fairly common design based on the old British Stay Calm war posters. I just used it to convey a beachy vibe that always makes you feel calm and relaxed. It's the beach, palm trees, rainbows; what more could you want?
This design looks great on all sorts of merchandise, from shirts to bedspreads to pillows and shower curtains. Here are some examples from my Redbubble store (click on any to visit the store):