If you follow the link from the
Ren'Py Home Page to the
OELVN Community Wiki, you'll find a page called
Free Background Art. The sites linked there generally give specific permission for you to use those images in your game.
Random images that you find on the internet, including Flickr etc, are almost always NOT permitted to be used in your games...
unless you contact the copyright holder (the photographer or whoever) and are granted permission directly by them. This is what I did for Elven Relations: all-bar-one of the backgrounds are either from
sxc.hu and under licenses that allow their use in anything, or anything noncommercial, or created specifically for my game. But one of them I searched around on Flickr, found a photo I wanted, and contacted the photographer, and he gave me specific permission for use of that one photo in that one game.
_________________
Author of
Elven Relations (IntRenAiMo 2007),
When I Rule The World (NaNoRenO 2005), Cloud Fairy (Cute Light & Fluffy, 2009), the
TileEngine and UnitEngine (LSF@5), and the fantasy novel
Ultimate Dream (NaNoWriMo 2006 onwards).
In development (progress slow but ongoing):
Elven Relations 2: Mermaid Liaisons: Story 96% done, script 75% done, character art 95% done, event CGs 60% done, backgrounds 50% done, customisation 0% done; demo available