Only users with full membership status can edit their posts, you should now find you have an edit button to the left of the quote button on your own posts.

Your image is displaying fine for me. Building models are unfortunately set by culture - a way to have different building images within a culture is to have different buildings within the export_descr_building file which are only available to a single faction within that culture. There's a series of knock on effects of that, however, and it's not open for all buildings.

Most of the UI elements (graphics etc.) are unfortunately done on a cultural basis. A notable exception to this are unit cards which are faction based.