You said you have left it up to the server to resize the images. Setting the width of an image, even if you are using an asp:Image control, does not actually resize the image. The image is downloaded to the users browser in full glory, then their browser scales it to the width you specify.
Maybe this article will help?
http://aspnet.4guysfromrolla.com/articles/012203-1.aspx
End the confusion.
Infinities Loop: TRULY Understanding ViewState.NET from a new perspective.
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