Hi Andrew,
here are a couple screenshots showing how they display for me in firefox:
http://jgarcia.hungry.jp/uploads/site.jpg
http://jgarcia.hungry.jp/uploads/blog.jpg
after installing chrome and trying that, I found that while not offset vertically the portfolio page and blog page are offset differently horizontally:
http://jgarcia.hungry.jp/uploads/chromeblog.jpg
http://jgarcia.hungry.jp/uploads/chromesite.jpg
If the background image thing is difficult I can live with the current system, I just thought that instead of aligning the top of the image with the top of the window and cropping off the bottom, it could align the bottom of the image with the bottom of the window and crop off the top, it didn’t seem to me like something that couldn’t be automated but I’m not experienced in this area.