On occasion I see a specific set of directions for a funeral that are attributed to the deceased: "[Name of deceased] asked that..." No flowers is just a trivial example; sometimes the directives are much more elaborate. It may sometimes be that the survivors are conveniently invoking the name of the deceased in order to have their own way with the observance, but I suspect that in the majority of cases the deceased has, in fact, imposed his or her will on the survivors.
Is this meet and right? Are funerals for the survivors, or should the preferences of the deceased -- whether rational or not -- take precedence? It's a complex question with no simple answer. I definitely dislike the notion of a soon-to-die control freak's writing a detailed funeral liturgy. One of my grandfathers wanted to write his will in such a way as to bequeath his estate to my grandmother -- and then go on to specify where she would (not "should") bequeath her own estate later. Thankfully, that's not how a will works.
Everyone must sort this out or choose to ignore the question altogether. I reserve the right to change my opinion, but I think I'll leave my funeral for my survivors to design for themselves. If they want my input, they can ask while I'm around. That said, it would be grand to throw a BBQ pig-pickin' 40 days out, with Steely Dan music.