They can either be from my own imagination if the idea is a more abstract one or from photos and images I collect.
For example a while ago I was reading The Graveyard Book by Neil Gaiman. This got me thinking of the shapes found within. Rectangular like a shawl. Oh a shawl based on a graveyard? That's an interesting idea. So I took my camera off to our local church and took some photos.
There are some head stones to give me some ideas of shapes and edging.
An old, rusty boot scraper.
I like to play with angles to spark some different textures
and to explore negative space.
Iron railings around some of the graves give me more ideas for edging and boundaries.
Once I'm satisfied I've got some starting points, I can go home and start to select the shapes that interest me the most. This is by no means the end of this part of the process. Quite often, I'll go back and take more pictures becoming increasingly specific if I want to explore something further. Other times I'll manipulate the image in Photoshop or I may cut it up completely and re-arrange it in a new order, pushing textures and shapes against each other.
Then I start to put the pattern together.