I am currently working on a CSS dominant style that truly flexes the power of CSS. On the plus side once completed designers will be able to use it's templates as a starting point for creating true CSS powered layouts. On the negative using the styleset will make using mods more of a challenge - particularly the ones that have template hooks.
That said here's what I plan.
95% matching layout to the vbulletin normal default. Some mismatches will be tricks possible in CSS that are difficult without - buttons glowing on rollover, CSS 3 dropshadows on the pop ups (Firefox 3.1 and Safari 3.1 only at this time). Some mismatches will be due to improper declarations being changed (pts are for printers, not screens). And then there might be a couple just can't make it match examples, but these will be kept to a minimum.
Except in IE 6 the popup javascript that vbulletin ships with will be turned off in favor of CSS popups which are faster and more responsive than their javascript equivalents. IE 6 will continue to use the javascript because it doesn't respect li:hover.
Three primary stylesheets for browsers that can pass the Acid 2 test, IE 7 and IE 6. No other browsers will be supported by this styleset (that includes Firefox 2 not being supported). The IE stylesheets will be corrective sheets in nature.
All images will be selected from CSS. The images that will ship with the skin will be 32-bit png files and gif files for Suckernet Exploder 6.
Keep in mind this will be a rather massive template set. Almost every single template in vbulletin will need to be edited (and there are around 800 of them). I expect to be ready to start beta in a couple weeks. I had intended to do this earlier, but vb 3.8 got announced.