So your beige is going to be a HTPC. Well, you can put it in a case meant for that reason, or build one from scratch using many availalbe case components. I'd suggest browsing through the mod guides for what people have done w/ their Beige G3's and see if anything inspires you.
MacBook 2GHz Intel Core 2 Duo w/ 2GB DDR2 RAM & 120GB SATA 5400RPM HDD
Canon Rebel XTI
Google Cr-48 Beta Laptop