Some sites to gather ideas:
http://creativestarlearning.co.uk/c/literacy-outdoors/
For some arts inspired ways into story making: http://storiesunderstones.blogspot.co.uk/
James Aldridge Exploring Art, Ecology and Learning, for bookmaking, collecting and inspiring ideas for storytelling: http://jamesaldridge-artist.co.uk/blog/
Julie Wilson, HT of Gigha primary is an excellent resource for all ideas to do with literacy in the outdoors. Her presentation from February 2018 shares research, pictures and resource ideas: Story Making, Story Sharing and Story Telling