Buildings aren't really an area I know a lot about, but associating a building with an image is a matter of placing the building card you want with the correct name in the correct UI folder. A good first step for that would be to unpak your UI.pak in your packs folder - use Vercingetorix's xpak programme - you'll find it on the Scriptorium.

As for making buildings dependent on (or blocked by) the existence of other buildings you need to use the and building_exists conditional (if your using complex name) or building_exists_min_level conditional if you want to specify a particular building level within that complex.

You can find some examples of that in the Compex conditionals for recruitment thread which is listed in the Index of Important Modding Threads stickied at the top of this forum.