lucy24 - 6:58 am on Mar 4, 2012 (gmt 0)
I know I could just make the top and bottom images 150px high, but I didn't think that was the best way to do it.
Well, that's definitely the first answer that comes to mind. Can you explain what the problem is?
Keep in mind that you can set the starting point for a repeating image. So if it's important not to chop the 150px image in the middle, position it at the top rather than vertically centered.
To double-check: You're talking about alternating images, in stripes, right? Not layered backgrounds where you have a 150-px repeat sitting on top of a 1-px repeat? One simple way to achieve that would be to make a div as big as the whole body, and assign a background to each, making the upper layer partly transparent so the lower layer shows through.