I think it is a personal opinion. Sometimes i say "velký" and sometimes "veliký" because a noun I use it with makes me pronounce it one way or the other. Sounds better is easier to pronounce, etc. There is one case, where "Veliký, Veliká" is used exclusively though and that is when we speak about a person that has "Great" behind their name. Ivan the Great, Katherine the Great, Alexander the Great. They are always Ivan Veliký, Kateřina Veliká and Alexander Veliký. Never "velký".
Sorry, but I don't understand why are you replying to me. Jamie08MD said that "Jé veliká" could not be translated as Is it big because that would be "Je to veliké?" and I told him/her that not necessarily, implying that Je veliká could actually be translated as "Is it big?", of course.