Your portfolio isn't bad, but as others said a lot of it is kinda bland, IMHO. Banners should "wow" you and make you feel compelled to click on the banner. No offense to anyone else in that business, but one of the best people in the business for the money is the following:

http://www.bannersmall.com/portfolio.html

I have used them, companies I worked for have used them, and many of my colleagues have used them and they do simply amazing work.