I thought I'd share with you a prospective banner I had recently mapped out, and its source image. I was planning to call it Petunia Planters. It's one that features planters, too, but after seeing your banner (so much better than mine), I decided to put mine out to pasture without submitting it. I've plenty of other ideas, and I love seeing variety, and imagine others do, too.
Here's the starting image
and the cropped version
Note added re the question of how much of my non-banner would show. I created it as 1200x150 pixels.