I think the most challenging cards to make are those for adolescent and teenage boys. Having only girls myself, I'm not even sure what boys in that age range think is cool, or more importantly, uncool. So I keep things pretty basic.
This birthday card was made for my 12-year-old nephew using the Cricut cartridge Martha Stewart Birthday Cake Art. Because the cake cartridge designs are simpler than many other cartridges, I find they work great for making quick cards. Fewer layers = less stress.
Thanks for looking!