I came across this piece of cloth hanging up at the Whitworth Art Gallery recently, which bowled me over. It's a length of stencilled 'adire eleko', mid c19th, made using starch resist and indigo-dyed cotton. It's from Nigeria, possibly a copy of a design first produced in Manchester for the African export market by Hendersons.
And another piece of inspiration from the Whitworth's Global Threads exhibition by Aboubakar Fofana, called Les Arbres a Bleus (2007, metal, pvc, sand and indigo-dyed cotton).
This explores the tree as a traditional sacred symbol in Mali and the long history of dyeing and patterning cotton with indigo.