Since GW doesn't offer a model for a Herald in a Chariot of Tzeentch I decided to make my own.
The first step was to get my hands on some chariot bases. I only had one that came with my Plague Cart that I used for my Khorne Chariot so I ended up tracing it and cutting a few bases out of hard board.
Next I had to figure out what to use as my chariot. I didn't have any spare Screamers so I decided to just use a really big Disc of Tzeentch. I rolled out some super sculpey and formed it into a disc and baked it. I then added a few green stuff spikes and stuck them on. I wanted the herald to stick up off the base even more than he would on the disc so I bought some aquarium scenery and broke it with a ruler to get a few small pieces of pillar.
I then mounted a metal horror on the pillar and glued it all together. To get the disc to 'float' I used a piece of plastic tubing and pinned it to the base and disc.