Ah, how the Fro-smut fans have departed in droves for J. K. Rowling's shores! (And elsewhere, but mostly to there.) I think that Frodo may simply have got too old to maintain his fresh budding-youth appeal for many of his fans. (Not, so far, the fate of a now-grown child actor from Cedar Rapids, Iowa).
The fact is, the character of Harry Potter simply is much younger. Perhaps that was a great part of the appeal of film-Frodo all the time -- not just his beauty, but his youthful beauty. I certainly noticed it, as did many of film-Frodo's female fans who were in or approaching middle-age. Suddenly besotted, we shrieked inwardly, "Heavens! I've become a pedophile!" (Not that older men ever think this when they pant for much younger women...)
Well, from my browsings tonight, it would appear that dear fanfic-Frodo has lost his original lustre for some, if not many (I was reading this off primarily slash sites, though other viewpoints were represented). Has he got too old -- even too accomplished from all those years of non-stop boffing in fanfiction? I suppose that, now, even he and Sam seem "a stodgy old couple" in comparison to the young bloods rising in fandom. Frodo must be getting to be almost as old as his book-canon age, in fanfic writers' imaginations.
Fans have become hungry for sweeter meat -- younger meat -- and have gone off to hunt it down.
(Well, lamb has always been preferred to mutton. *snerk*)
~ Green Ghost's, In the Tower, her Cirith Ungol Frodo.
While snooping around, I found some fascinating items lying around in the LJ's of these fans and writers. Just look at this! I found this manip, made from a well-known (and cherished) Frodo-in-bondage screencap from RotK. On the site where I found it, it was credited to, "Green Ghost." Well, thank you, Green Ghost, wherever you are!!!
As you will see, this screencap has been "finessed" to show Frodo as CANON Frodo in the Cirith Ungol scene. That is, he is not wearing anything. There's a healthy dose of red light added to it, too. (Very canon touch, again.) Clone-brushed away are film-Frodo's trouser tops. And no underwear waistband is peeping out. Bathed in ruddy light, this Frodo is wearing nothing, as per the book. I am confident you will feel the same rush of vindication and pleasure at the sight of "book canon restored" when you have viewed this manip....RIGHT! (*knowing grin*)
Edited to add:
Is this a pencil sketch, and not a manip (see Ariel's reply below)? I just saw it hosted at The Green Door per Mariole's link below, where it says it was made with Paint 7. Amazing finessing, though.