Old UNIX Systems

I've been working on getting shelving installed in our Garage, and as a result, I've been digging back to some systems that have been buried. Right now I'm moving a bunch of Sun hardware and it hit me. What good are old UNIX systems? I'm curious, what are people using things like Sparc 2's through 20's for? Or even Ultra 60's and older? Part of the problem I'm looking at is that you can get something like a Raspberry Pi that will cost a fraction of what a Sun system costs to run. I won't ask this about my two SGI O2's, as they're artwork. BTW, I'll be honest, I'm actually using two Sparc 20's right now. Each one sits on top of two Record Crates, and acts as a speaker stand. They've filled that role for several years. Somehow though, furniture and artworks really aren't the uses I'm looking for. :-) Zane