I don't personally have information, but Delta and Fillmore both have a public libraries, so one of the first things I'd do is to contact the reference librarians at each facility and ask about any photos the library might have of which you could obtain copies. The librarians would also be apt to know of anyone locally who has a hobby of photography, who might have images, and of the existence of a city or county historical society.
Both communities also have newspapers, and it'd be worth an email or a phone call to see if they have any stock photos they could provide.
Finally, it's likely that Clear Lake and Lynndyl had "standard depots", so if you cannot find photos of those specific details, it might be that the railroad could provide you with information on what plan was used, so that you could come up with a reasonably close approximation of the actual depot.
ns
