I used to have stand alone tubs on a utility storage shelf. But I eventually upgraded to a rack due to convenience.

I don't have any photos, but it was just tubs lined across the shelf w/ flexwatt running under all the tubs. One strip of flexwatt for each shelf saved a lot of money compared to individual UTH on each tub. Not to mention I was able to attach less cords to the thermostat at a time this way.