I'm converting 4 20G talls into vertical terrariums with front opening doors, for my crested geckos.
I decided I wanted to try out the conversion kit products sold by http://www.junglebox.net/
I haven't received them yet, but I'm planning on posting a whole "DIY" thread in the future as these tanks are going to require drilling holes through the side (soon to become top) glass for mounting nozzles for a Mistking system, installing the previously mentioned doors/ventilation, a custom shaped tree fern root background, drainage AND soil, and plants etc.
I'll let you know how the conversion kits work out for me.