Coming from a non-DG, I think your website looks great! The picture of you and your mom is so cute
You obviously put a lot of time and work into that site! Personally, I think it would be extrememly rude of your E-Board to tell you to change it all. Youre right about all points mentioned - the site is a place where PNMs can come and see what DG is all about (when I was rushing I know I checked out all the sites of sororities on my campus- and was very impressed!) where alums can catch up on the chapter, and where girls in the chapter can see whats going on. i would definitely explain all of that to yoru e-board.
If the national webmaster approved the page - then there should be no "offical" reason for them wanting it changed - just out of their personal preference, and well it's yor job to make the website, so they are going to have to live with your decisions.
I say stand firm in your decision. If they absolutely want it changed and will not compromise, tell them you don't have the time to put into a SECOND site and they need to find someone else.
Just out of curiousity, how does the rest of the chapter feel about the page?