I applaud you for looking at web standards. While there are sometimes this makes things more difficult (as you are finding out, design time is one of them ;) ), the long term maintenance of the code will probably more than reward you for the effort.
I have a couple recommendations that will hopefully make this easier for you. One, I've found it easier long term to work with CSS in an external style sheet (a .css file) rather than using inline styles in this way. To some extent (usually not as much as advertised), this may reduce the amount of "bloat" in your webpage. However, it does do one key thing for you. It absolutely helps with code separation and thus anytime you want to change the appearance of the webpages, you can head straight to the css file(s) and make the changes you want. Long term, I think you'll be shocked at the extreme changes you can make either to your CSS file or to your HTML code without having to do much work on the other. This is a huge way ease your maintenance of the site.
Two, I would try to go with background images all the way around. It may not be a big deal, and if using <img> tags is the only way you can get it to work, I'd do it. But by specifying the position: attributes of the background images for you divs I believe it's not that difficult. Granted I don't have much experience with that technique but I can offer two pieces of advice. One, I believe the examples at www.csszengarden.com
are done without any image tags of any kind, yet many of the layouts achieve some amazing image effects. While I may not be much help, ;) I bet studying some of their examples would be. Second, if I remember correctly you can adjust corner images by using a combination of postion: top/bottom left/right. You can adjust for the unknown length of the sides (and even the un/known length of the top and bottom too) by using backgroun-repeat: repeat/repeat-x/repeat-y. Repeat-x tiles the image horizontally for top and bottom image borders, repeat-y tiles vertically for borders on the side, and repeat tiles in both directions (used for a background tile.
Hope that helps
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