As promised, here are some pictures of my version of the Silver Tower of Tzeentch. It's still in progress, but I'm liking the look so far. The stompa on the left and the Fire Prism on the right give some idea of size. Without any type of base yet, from bottom to top of the crystal is slightly more than 12".
When I scrapped my original idea, I sat down and was talking to my girlfriend about what I wanted to do with it. The comment was made that I'd like to use some sort of twisting tentacles to maybe hold up the center gem. She then had the idea to use masking tape to make twisting tentacles up the sides of the building. This was then incorporated to look like they are thrusting out of the ground.
After a visit to the local game store, I managed a good score with the tyranid bit that is currently holding the crystal, and it got incorporated in. A few left over spikes from some Chaos Terminator Lord kits, and a Possessed kit helped to adorn the top, and some of the many tentacles and spikes left over from the Chaos Spawn kit work around the bottom.
I still want to get some Tzeentch symbols on there, and will likely be doing some more scratch work for those. But for right now it's going to look pretty as is on the shelf until school is done in a month.