Beige G3's make good support machines. RAM and cheap HD's can be found for upgrades, they have built in ADB and SCSI to connect old stuff with and built in networking. I have a CDRW in my Biege G3 tower so I can burn images for older machines in the collection.

My desktop G3's tend to get some kind of PCI video capture card and are dedicated to that (Targa 2000 as an example).One of my B&W G3 with G4 upgrade houses a Matrox RTMAC setup and the other one was my main Mac (g3-400, 1GB RAM) until I recently got a Quicksiler 2002.