Gotta say, I usually follow the same method as Ariel... I usually work up my graphics in a PSD file then setup a blank "Skin Folder" with:  skin.html   skin.xml   and   skin.css . I manually slice out the images I need and assemble them in Dreamweaver, test the layout then add in my Tokens, upload the basic skin and then I usually edit the CSS live on the site so I can see the changes as they happen, then just keep my code sync'd and work out the kinks from there...

Regarding the style you're going for with the containers, it may be a bit tricky, I have not yet pulled off a container with rotating / interchangable graphics... The only way I could think of right now would be to make a different container for each graphic (teddy bear, clown, etc. with whatever you're using) other than that, I'd just reverse-engineer the containers that came with the default skins.

As far as CSS goes, I've been working with it for years and I still haven't mastered it, I usually keep a copy of O'Reilly's CSS Pocket reference handy (ISBN# 0-596-00777-9) and a Visibone Reference card ( http://www.visibone.com/products/cardcollection.html ).