Oh, and incidentally, if you can locate a mercury-vapor diffusion vacuum pump and a few other bits, you can build a particle accelerator ("atom smasher") using the output from those things as a beam source, that will give some pretty neat results. You have the basis for a great "mad scientist's lab" there, already! :yes: :thmbsp: Oh, and be sure to dredge up a Wimshurst generator, a few Jacob's ladders and some huge leyden jars and such, just for added visual effect. Very, very cool... especially at Halloween when you put all that stuff near the front door...
EDIT: I just read your comment about thinking that there was a Van de Graff near the base of the one Tesla coil. That wouldn't be surprising; you can get some spectacularly ramped-up lightning bolts off of the combination, if you hook them up right. Whoever put those things together, was seriously into some high-voltage "fun". Are you sure you didn't get them from the estate sale of someone recently departed...?
Oh, and your idea of just putting them on a shelf for looks is an excellent one! They are GREAT for that, and while they can be fun otherwise, they can also be genuinely dangerous. If you really want to have fun with electricity, stick to the Van De Graffs --they are much safer than Tesla coils, which easily generate dangerous levels of electricity.