So, we've had a long chat, and I now now more about GoT than I did 24 hours ago, so thank you!
Not that I'm sure my life is much improved by all this GoTology...
Anyway, Lust chose for the title of this thread 'Stories or depictions of Game of Thrones
characters... etc'
That the characters were young at the beginning of the series does not imply that they were under age in the scenes reproduced in this thread, especially those from Deviantart. The actresses are also now aged above the rules threshold.
As the link that Naraku posted points out the TV producers deliberated uprated the ages of the characters to sidestep this issue themselves, and clearly the visuals in the image relate to the series, not the books.
Eulalia put it better than I can:
"We deem it unlikely that the content of a well-known tv series would cause us any trouble,
so long as members refrain from dwelling on the young ages of characters or actors,
and especially from using images from the series in manips etc. that could be in breach of our rules. "
So play on, we're happy.