With the Apple emblem right in the center it requires a bit of creativity to come up with something that looks awesome, but it’s definitely doable. The apple emblem is plastic and protects the wireless antenna, however it can be masked over to protect it from the laser.
Any vector artwork can be laser engraved onto an iPad. Shutterstock.com has 1000s of images of anything you might be looking for. They generally cost around $10 per image, or you can buy a subscription. Use this search box to get started browsing: