I hope my comments below are helpful and not seem at all like Im putting it down in any way
- I would change the images to text and use CSS to create the style as such (Better for SEO) unless you were going to do that anyway.
- Maybe make the navigation text size smaller as it looks a bit full at the moment, or take some of the links off to use else where OR drop down menus.
Background - One thing on the background, on the corners at the bottom of the red I would take off the corners as it would look nice and clean. So it will be one line stopping at the base of the red.
- I would make the corners smaller in size so not such a large curve as a smaller style is more web 2.0 and would look nice
- If you add some line height to the general site (Within body tag of CSS) this would help with the reading of the text
- Make sure areas are aligned with each other
- Add some spacing around your login form to clean it up a bit.
- Also add a favicon which is always good to have.
Hope this helps, and you dont think I was being harsh in any way Its just my views anyway.