I store my keyboards on keyboard rigs that I either buy or make myself. If you're going to collect circuit bent instruments and toys then you'd obviously want to play them, won't you? The best way to store them would be to setup a room to have racks and rigs to display them and provide easy access to play them. Also, a desk or studio console would allow playing of the instruments as well as storing them for display purposes. A stereo system or mixing desk would also be great to have all the toys linked up and plugged in ready to play through the amplifier... it doesn't have to be professional equipment, but possibly a boom-box or home theater system.
If you only collect the things for the purpose of owning them and looking at them, then storage would involve putting them on display on permanent or mobile shelving... or if you can afford it, perhaps glass cabinets or deep book-cases.
I personally don't see the point in building a collection of circuit-bent toys that you don't use or play. If you want to look at them, then pictures and posters would be just as effective! LOL... but you'd be silly just to sit there and stare at a circuit bent toy and dream about it or fantasize about it when you can simply pick it up and PLAY IT!
Just my two cents worth.