Oh, yeah, I'm also keeping most of the cards very clean and simple in design. This is just striped paper on cardstock. After I found an ink that coordinated with the stripes, I also used it around the edges of the cupcake. The cupcake is attached to the card with dimensional adhesive, so it stands out a bit.
I haven't made many gate fold cards, because I usually don't think about it. I tried to choose a lemon-yellow cardstock, and I paired it with this pink/yellow checked pattern. Again, I used the same ink for the stamp and the edges. The narrow ribbon holds the card together.