I planted a couple seasons back. I never thought about incorporating some "height" into it until I was trying to find a place for my butterfly house. Now I plan on putting a butterfly house or birdhouse behind my windowboxes each year! It really does helps create a focal point among the jampacked flowers!
The year this photo was taken was the year (in April) I lost my job. I had to compromise because of no income and went around the yard digging things out such as ferns, and golden moneywort (I thinks that's what its called). The rest of it is mostly New Guinea impatiens, Dusty Miller, and Fuschia. The butterfly house I found at a local garden center for $6 (I love its tin roof). Here's a pic of the windowbox on the opposite side (one is on each side of our main entry door)! Thanks for the compliments!