Is it worth a back-end developer's time to get into web-design and HTML/CSS
functionoid: I'd say learn html/css and along with that concentrate more on usability of the website. To be really good at creating graphics and flash for websites could take some time. So I'd say definitely learn HTML/CSS also learn the usability aspect of web design and out source the graphics part. May be for this project you might want to outsource the html/css also.