Could somebody give me some guidance?

I'm trying to work out whether I should post captioned images - I recently had a comment from another group where I was posting stories similar to my captions, but with words instead of modifications to the pictures themselves. I can understand if there is an issue with that, since the photos themselves are unchanged, but I thought there was some law about lawful use of copyrighted material for artistic (well, comedy, fiction, literary, etc.) use? If anybody knows, please clue me in - since I haven't a cluon (the tiniest particle of a clue :) ) at this point!
XOXOXO
Angel

The Accident in the High School Chemistry Lab (this girl is so sexy, and, believe me, she's over 18!)

Harry and His Mother (optimized images)

Elliot's Virus

Finally, a comment!

Sedra, I love you! I can post again :)
Laissez les bons temps rouler!

I'm going to wait a while

Before I post again - it doesn't look like my captions are very popular, there's been no comments on them!
If somebody comments, I'll probably start posting again - I have lots of captions!
XOXO
Angel

The Neighbor